My (limited) drugs experience:
First tried weed around age 17. Usual scenario, was at college, friends were doing it etc.
Found it great at first, giggly, relaxed, happy times.
Fast forward a few months of smoking it casually on and off, it kind of turned on me.
Paranoia, hallucinations, panic attacks, 'whiteys', you name it.
I never smoked it regularly or in large quantities but I feel it unleashed some mental health problems that I think were probably always there beneath the surface.
Found it very easy to quit luckily.
In my mid twenties I tried cocaine after being surrounded by it for years, mostly in clubs, at parties. I'd say I did it once or twice a month. I never once suffered any side effects from it, except good ones 
I stopped using it after a few years though. Got sensible.
Again, I found it very easy to stop but boy did I love it while I was doing it.
So for me, weed equalled a fucked up big time, awful, mind altering experience yet cocaine I found to be totally enjoyable with zero negative effects.