I mean, obviously it's a bad idea. Psychedelic drugs are known to cause severe hallucinations that can easily make the user feel many different emotions that might endanger user or people around him/her. Person can feel suicidal or homicidal and I don't really have to explain why that's bad. Long term side effects include anxiety, panic attacks, paranoia, aggressive and violent behaviours, etc.

Also how about the fact that you can literally go into coma if you overdose? I'm surprised there is even a discussion about this, anyone who uses drugs like these on a regular basis are bound to go insane at some point in their life.