I gave up dope about 10 years ago.  I combined it with a move away from a lot of the friends I used to smoke with & obviously everything that goes with such a big change.

As such I didn't really feel the pain of withdrawals.  The main thing for me was getting out of the circle that lived their life in this way; constantly smoking & never going anywhere.

I sound like a Tory clown now, but looking back I can't believe I wasted so much of my life on that crap.  It sucked the life out of me. 

It's hard to quantify the impact of giving up as I combined it with moving towns, obviously that in itself had a dramatic effect on my life.

I'm not sure I would have been arsed to pursue my goals had I kept on smoking, irrespective of my environment.

Good luck.