But the key is not to "quit" something that you now do. The key is to be someone different, someone new. Instead of seeing yourself as a smoker who is being deprived of the very thing that defines you--smoking; see yourself as a non-smoker. And then live into that vision. Instead of making it a negative thing, something you have to "quit'. Make it a positive thing, be someone new; be a person who doesn't have that bad habit.
Sure, it may still be tough for a little while, but adjusting to a positive state is much easier than accomplishing a negative goal.
Of course this strategy applies to any changes one wants to make: a new diet, new physical routine, new spiritual practice, new behaviors, whatever. Remember that whatever you want to accomplish, if it is humanly possible, someone has done it before you. You can do it too. Just establish that vision and live into it. Don't just dream it, be it.