Not heavily and not hardcore drugs, but after non-stop everyday use I found that many like alcohol become very boring and start to make me more and more sick. Well how badly you truly want to stop is a big determinant, but realize you are going want to stop even more later on so keep that in mind.
Here's some advice that workded for me though. First start associating drugs and everything surrounding them with disgust, don't associate them with any positive ever. Now simply limit yourself to the minimum of what you think you can reasonably handle and just work on that. If you give in, just tell yourself next time, it'll happen eventually if you never completely give up so no need to get paranoid over it. Distract yourself constantly. A day or 2 off from everyday use can be a big accomplishment, then every other day and you will be most of the way there. Keep in mind you will probably have to quit forever at some point, especially coke and opiates. Indulge in other things using that drug money. Teas, coffee (powerful stuff), or even chocolate, gum, candy, really spicy food = endorphin rush, buffets, or even better, distractions that take up your time like going to move theatres/cool performances. If you get an urge, go for a run, bike, learn to skateboard, swim, workout, dance crazy. Releasing adrenaline and endorphins work great and you will start to feel better after, healthy = mental strength and more dopamine. Or you can clean, organize, rearrange your place or anything constructive, it will make your mind more clear and in control. If you manage to do one of these things instead, don't save that drug for later, throw at least that much away as if you used it, you will be doing the opposite of wasting. If you have anxiety look for linden tea, it's the most calming, relaxing tea I've ever had but there are others, I buy my from mexican shops. Also, some good weed is the best drug if you don't have a bad history/association with it. I often find it leads me to want to do other drugs, so what could help is to just have a ton more weed to smoke instead of other drugs (can never be too high), even better is to find a good distraction you can do forever when you are high. Another very good way is to have someone who might care help you, as long as you won't get super pissed at them later. I hear meditation or just breathing exercises is super powerful. Lastly don't smoke cigarettes, bad for mind, body, and I can think of 10,000 better ways to die than cancer. Think of replacing the drugs with something good so you won't regret having given it up when you have stopped. Hope you try some of these things, good luck!