What's the best way to stop doing drugs when you feel pressure to keep doing them?

I'm done with doing drugs. All my friends do it (weed, DMT, coke, shrooms, etc) and they get annoyed when I don't partake. I'm just a boring guy that wants to work on my career and make some money. I used to do drugs all the time with them but I don't want to do them anymore. How do I make them understand?