I began smoking pot at 15 years old and smoked almost daily for approx 20 years...and when I finally stopped, I found many of my mental and emotional problems simply went away.
The things that used to strongly effect me, things I used to obsess with...I now see as small stuff, barely worth giving a second thought.
I have a much lighter outlook and am more optimistic in general.
I've noticed that my friends who are still smoking pot seem for the most part to be emotionally stunted...stuck in their own little worlds and preoccupied with the same sort of little crap that used to drag me down.
Still, I have nothing against smoking pot occasionally. I don't think it has the same effect as smoking regularly.