Congrats on quitting. As hard as it is to quit the rewards afterwards will be greater than the stress you feel now.

I smoked pretty heavily for 17 years before I finally quit. Now it's been over 6 years since I've had a smoke. Quitting was one of the hardest things I've ever done but I feel so much better now. Back when I smoked I used to do a lot of serious rock climbing and mountain biking. I was pretty good, better than your average person, but could never get to that "great" level. Now I really think that the cigarettes were what was holding me back. I wish I had never started but like everyone else, I was young and stupid.