I'm going through my first week of quitting. So far, it doesn't feel too bad and fortunately I don't seem to have replaced the habit with anything else bad (e.g. overeating) - but it has only been a week. Out of curiousity, how much of an improvement was quitting smoking for you? So far, I've noticed at BJJ only after a week of quitting, a big improvement. Perhaps its mind over matter and I'm the same level of fitness but I feel that I have that extra bit of stamina that I wouldn't of had a couple weeks back.