NC'd for this!
My DSis were talking about our heady young days and the 'dabbling' we did 
For the record, I'm talking a few episodes of stupidity many many years ago, and am not in any way endorsing drug use, in fact this thread could be seen as more of a cautionary tale.
She told me that once she took magic mushrooms and had a completely awful experience where she felt nothing was real and she would be stuck in the 'dream' forever. She honestly never thought she'd get out. Never did it again.
I had a horrible experience on pills when I thought I was two different people. I kept switching between the two people and it was awful, I had no idea who I was or what was happening and it lasted about 3 hours
Never touched anything ever again, that was about 15 years ago.
What's your worst experience?