I hate that you had to quit, but if it's for your back health, well: BRAVO!

I've been in the same position for a different health reason, so here are a few GOOD things about having to lay off the MJ for a while:

Firstly: the money. You're gonna save a ton of it.
Second: tolerance. Once you do start smoking again, you'll be like a kite.
And, this was my personal favorite: DRIVE LIKE A MADMAN! When I wasn't smoking I sped, ran stop signs, never got in a crash, never got pulled over, and never worried about police.

I do hope that you feel better soon.
Read some awesome books. Do yoga!