take a vow that you won't smoke for some time,
like 1 week or 2 weeks.
and if you break your vow, then just start again, and take another vow.
suppose u don't smoke for three days, and then smoke again,
then u just take the vow again, and not smoke for a week.
and go on increasing the span.
don't say: i wont ever smoke again. coz the next thing u'll do is light a cigarette
and breathing exercises can be very helpful too.
when i started yoga, i couldnt even stand smoke coz it's kinda disgusting. :D