I don't regret doing coke or MDMA. Both of those things, I was able to keep under control. I mean I can't really AFFORD a cocaine habit, and the high is far too fleeting for my taste. I will say, however, I do regret doing MDMA multiple days in a row. Don't do that, the following days will be catastrophic to your mind. MDMA is super fun though, IMO. Just gotta limit it, as you should with everything else. If you have an addictive personality, I can't, in good conscience, recommend trying cocaine. But MDMA, to ME at least, didn't have that addictive quality. Possibly because of the aftermath of using it 4-5 days in a row, but the first few times I used it were spaced pretty far apart, and were no noticeable after effects from it. But everyone's brain chemistry is different. It's good that you're aware of your addictive personality. That could save you, if your decision making skills ain't too shabby. Moderation is the key to everything. Some can do it, some can't. I can use certain drugs once in a blue moon, but I tell ya what, opiates grabbed me by the balls and wouldn't let go. I'm currently detoxing a 2 year, 150+mg a day oxy habit. It got so serious so quick. Should have wisened up a lot sooner, and I wouldn't be in such a physically and mentally painful situation right now. Everyone has their drug of choice.
So, to answer you question entirely, kind of. Lol. I regret doing opiates is all I regret doing. Everything else was and still remains a fun time when it presents itself. But once you try a certain drug, and you notice yourself thinking about it often the next day, and/or considering hitting up your source again, I'd say pump the breaks, and think about what you're doing.
Sorry if that, at all, went off topic, but I've been hittin the trees til I turn Vietnamese, and caught myself forgetting the main question in this thread.