The only way I remained sane was to meditate. Stoned or not, it's a great way to release all your bad energy. It's a real trip to go past normal meditation into deeper layers. That's the reason I stopped using drugs. I found that I could see and feel anything that I wanted through meditation. You also develop an ability of clairvoyance (psychic ability) through higer meditation. I recommend you guys to read Astral Dynamics by Robert Bruce. Here are some concentration exercises by Robert Bruce that I use. BTW, if you have ADD.. meditation will take that problem away from you
Concentration Exercise (1)
After image retention: Relax, calm your mind, and look at a candle or a light bulb. Place this light in front of you, a couple of feet away, and stare fixedly at it for a minute or two. Close your eyes and concentrate on the after image this will generate behind your closed eyelids. Try and keep sight of it for as long as possible. Use breath awareness to keep the mind clear, while you are doing this. Try and make the after image grow, instead of fading away.
Concentration Exercise (2)
One point stare: Pick a spot on a wall and gaze at it. Don't focus on it, just gaze at it gently. Clear your mind of ALL thoughts and forcibly hold it blank. Concentrate HARD, on breath awareness while you are doing this. When you feel a thought beginning, push it away, don't let it finish! Hold this for as long as you can. Do this several times a day, or more if you can.
Concentration Exercise (3)
Energy breathing: Sit and relax. Close your eyes and clear your mind. Do the breath awareness exercise and imagine the air you are breathing IN is brightly coloured energy of your favourite colour. Imagine the air you are breathing OUT is a murky Grey, full of toxic waste. This is a purification exercise. It stimulates your chakras into absorbing energy on the inhale and getting rid of negative energy on the exhale.
Note: Try your best not to tense up while you are doing these concentration exercises, it is ALL mental. In the beginning, it may feel as if you have to tense your mind into a tight ball to stop it thinking, but in time you will find the opposite to be true. When you get used to it, clearing the mind is VERY relaxing.