First we'll talk about illness, as they're are many different types of it. Some are temporary like catching a cold, others can be permanent, such as arthritis or fibromyalgia (like me), and other diseases that cause constant pain, or things like asthma, that come and go.
If you are suffering from a nasty cold, or the flu, it is not advisable to perform any magick until you have fully recovered, especially if you are taking some kind of cold medication to help ease your symptoms, unless it's an absolute emergency. However, during your illness, you can dramatically speed up the time it takes you to recover through meditation, concentration & visualization techniques, that every good Witch practices, at least once a day anyway. Think about the symptoms you're experiencing, and send a strong signal to your sub conscious mind to use it's strength to rid you of the dis-ease you feel. Not disease, DIS-EASE. As you meditate while lying down, have only one thought going through your mind. Picture your body vital and in perfect health. Use your powers of visualization to clear away the dis-ease that has entered your body. Release yourself from any discomfort you are experiencing, and tell your body to do whatever it has to in order to get rid you of it.
If you suffer from a permanent, or incurable condition that causes you to experience severe discomfort, it's best to only perform magick when you feel at your best. For example, if you are experiencing an enormous amount of pain, do not perform magick until that pain has subsided to the point where it is not overwhelming your mind, and you are able to fully concentrate on whatever spell you are planning on doing. There's no point in trying to perform a spell when you are subconsciously thinking about how much pain you are in. It will just cause the power you raise to go hay wire, and be completely useless or in some cases, be dangerous. If you are suffering, but have an urgent need to perform magick, you must be at a point in your meditation skills that you can easily drop into a deep theta state, which will allow you to focus on the spell. Otherwise, don't bother until your pain, or discomfort is not at the forefront of your mind.
Magick and Medication
Other people must take one, or more different types of medication everyday for a variety of reasons from depression, to pain management. When you are put on a new medication, you should not perform any form of magick until you know how the side effects of the medication effect you. If the side effects are such that they interfere with your concentration, visualization, and meditative skills to a great extent, it is not advisable to perform magick under those conditions, as they will severely effect the energy of the spell.
Thankfully, many medications side effects that need to be taken on a permanent basis only last for a few weeks, until your body becomes used to having it in it's system. Once that occurs, you are free to return to your regular spell crafting. If you need to take medication to reduce stress, they can effect your concentration as they can fall under the hallucinogen category. These are medications such as Valium or Xanax. In those cases, you must use your true and best judgment, and ask yourself if when you feel the effects of them, if they are enhancing, or decreasing your level of concentration. Normally these drugs are taken for stress and help the person relax or sleep, but if you feel too 'high' or euphoric when you take them, you shouldn't perform magick when you're on them.
Drugs and Magick
I must be honest and admit that when I was much younger, I experimented a bit with street drugs like acid, DA, and cocaine, and never got addicted, had a 'bad trip', or had any bad side effects from them. But performing magick when I was on them didn't even cross my mind, and should never be attempted. The one thing I always did do, was wait until other people took it, so I could see how it effected them, just to be on the safe side. But the street drugs that are made today, such as ecstasy, and crack cocaine are literally 10 to 20 times stronger than what I took those many years ago, or didn't even exist!
While I'm sure many young people reading this will now think I'm being a hypocrite for saying this, I beg you, to NEVER take any street drug such as the ones I mentioned, or other life threatening ones like heroin. Even marijuana can be laced with deadly drugs such as heroin. In my day (about 20 years ago), street drugs were mixed much more carefully, and not mixed with other dangerous chemicals like they are today. They were also about 10 to 20 times WEAKER than what's on the streets today. You should avoid them altogether...period and NEVER take them under ANY circumstances.
I had a few very frank discussions with my young niece about taking street drugs. At first she thought I was being a hypocrite, and just a paranoid old bag trying to scare her. She was right about one thing...I was trying to scare her, and for good reason. Let me share a story with you that I hope will get my point across as to why you should NEVER take street drugs.
One night my niece went to what's known as a 'rave' party, where ecstasy was being handed out like candy. Due to the talks I had with her, she wisely decided not to take any ecstasy that night, and just drank alcohol. Unfortunately, most of her friends thought she was just being an idiot for passing down free drugs. People, especially young kids that have very insecure personalities, are particularly susceptible to having 'bad trips' that can last several hours, and because everyone else is high, and too afraid that they'll get into trouble for taking drugs, they don't know what to do, and won't call their parents, or an ambulance for help.
One of my nieces friends started showing signs of having a VERY 'bad trip'. My niece did her best to try and calm her friend down, but she got more and more paranoid, to the point where her hallucinations showed people to be horrible monsters that she thought were all trying to kill her! She finally ran screaming out of the warehouse down a barren back street. My niece ran after her to try and help, but Linda (her friend) thought my niece was a monster as well, and just kept running, and screaming that a monster was trying to kill her. One of her high heals fell off, and she continued limping away, falling and getting up again. She finally fell down scraped and bloody, and couldn't get up. My niece had called an ambulance from her cell phone while she was running after her friend.
When she caught up to her, she began to try and talk her down, and get her to calm down. But her efforts fell on deaf ears. Linda was now convinced that my niece was still a monster, and that she thought my nieces loving strokes of affection were bites from a monster, and now hysterically screamed that she was being eaten alive! This continued for some time until Linda finally calmed down and fell asleep in my nieces arms. The ambulance showed up minutes later. Only Linda wasn't sleeping, she was dead. The ecstasy, caused her to literally scare herself to death.
After that horrible experience, my niece, and everyone she knew never took any street drugs again. And I hope that this true story will scare you into doing the same thing. All it takes is one 'bad trip', or one drug laced with the wrong chemicals, and you could die as well. Is your life worth so little to you that you'd risk it just to have a good time at a party? I truly hope not. And I hope all the parents who read this will get their children to, and the young people who read this story will tell their friends about it, and as many people as they possibly can. This is no joke. The drugs on the street these days are just as lethal as a loaded gun, except you die a much worse death from them. I beg you, don't risk your life by experimenting with today's drugs. You're putting your life on the line every time you do, and you could DIE just as easily as Linda did. She was only 17, and had a bright future ahead of her. She only took it because 'everyone else was'. Be smart. Don't risk it. Your life is worth more than having a night of fun at a party that could cause you brain damage, seizures, or like in Linda's case...death. DON'T TAKE STREET DRUGS!!!! EVER! Got it?? And if one of your friends is idiotic enough to take it after reading, or hearing about this, and is having a bad trip, or showing any signs of sickness, call for help immediately and worry about getting into trouble later. You probably won't, you'll most likely save someone's life, and learn a valuable lesson. And while were on the topic, don't ever leave your drink unattended as a guy can easily slip a date rape drug in it. And don't ever accept a drink from a stranger. Only if it is a beer that has not been opened, or touched by anyone but the bartender. Be smart. Be careful, and take care of yourself, and your friends by printing this out, and forcing them to read it.
In loving memory of Linda Campbell 1988 - 2005.
Taken from us too early.
May peace and love be surround you.
You are loved, and will never be forgotten.
May your story prevent others from the same fate.

I have experimented using it in small doses when I meditate, and find in very low doses, it can be a helpful aid in getting me in the mood to meditate, when I otherwise would have done something else. In stronger doses, it completely interferes with my concentration, and makes it impossible to even reach a mild state of meditation. On the whole, I do not recommend using marijuana to help aid in meditation, or concentration exercises of any kind, and definitely not for performing magick. In experiments using it for divination purposes, I also found it totally ineffective and confusing, therefore I don't recommend using it for that purpose either.
I also experimented using marijuana while scrying. I scryed for an hour without it, wrote down my visions, spiritual messages and impressions, then smoked some the following day at the same time (at night). When comparing notes from one day to the next, I found that it dramatically increased my ability to scry, see visions with much more clarity, and receive messages from the spirit world with much more clarity as well. I can understand why natives would smoke this plant for those purposes. If you live under conditions where you are legally allowed to smoke marijuana, I only recommend using it for scrying purposes while using it for your pain management and/or nausea. Nothing more, and definitely NOT for performing magick of ANY kind. It is not worth buying illegally just to scry, unless you want to end up in jail, and with charges against you that will haunt you, and prevent you from getting many jobs for the rest of your life.
As far as alcohol is concerned. I don't recommend drinking any alcohol before performing magick, divination, or scrying. However, if you are particularly stressed out more than normal, I think a small glass of red wine is okay to drink before hand, as it will aid in your relaxation. Besides many doctors around the world agree that drinking one glass of red wine (not white) a day, actually aids in your health! As always, use your own discretion.