I've been a moderate smoker (1 pack in 2 days) for about 15 years and one day I just decided to quit. I had some nicotine withdrawal for a few days and some mild muscle spasms but other than that no further complications like SOB, excessive coughing etc... Actually after the 3rd day I started feeling MUCH better, I was surprised cuz all my friends who quit told me I will be experiencing whole lots of problems, but I'm glad I didn't. Anyways, just felt like sharing my story. By the way, I went to gym the week I quit maybe that's what helped me avoid the complications. Good luck everyone! :-D