Just to add some helpful information, since I feel I can quit cold turkey on occasions when I want to, I thought I would say what helps. It may be some of the same info already mentioned, but without going through all the pages, any new comers to this thread might not see them.
You have to have a reason for quitting. Make that reason seem extremely important to you, whether a family member wants you to quit, you want to have better health, or you want to save money. I would say pick ONE to focus on and let the other reasons be icing on the cake when you quit. I'm a huge fan of Bruce Lee and look up to his level of dedication, and in his book, there is a quote that is in there saying " You can act into a new way of feeling, but you can't feel into a new way of acting". ACT like you are mentally tough, and you will become mentally tough eventually. ACT like the reason you choose to quit is an extremely important reason to you and what directs your everyday actions. It's ok to be fake or lie to yourself about how important it is to you. The longer you fake it, the more it will become real. If others know you are trying to quit, and they ask you how you are doing, tell them you are perfectly fine, even if it's lying. Say you haven't thought about it at all. If you keep lying to yourself about it, you will start to believe it. Also, act like someone is watching you at all times and you don't want to let them down. You are more likely to let yourself down than someone else.
When I made my decisions to stop (I guess I can't say quit) I would go an average of a few weeks to a couple months with no dip until I decided I just wanted to do it again out of boredom. It does get pretty boring sometimes on deployment. I would still have my last can, and I would say this is my last can and treat it as my last can. I would spare it as much as I could, and try to savor the last bit of it as if it were a long goodbye. It prepared me to know I wasn't going to have any, kind of like bringing closure to it.
IF you were like me, and you have friends or co-workers around you that dip, everyone would occasionally bum a dip off each other. Get them involved by telling them you are quitting and to not let you bum any off them. If they are anything like the people I am around, they would get pleasure in your pain when denying you any of theirs.
Look at your lip in the mirror. It heals pretty quick, but when constantly dipping, you would normally have that white wrinkly patch. Everyday you don't dip, it gets noticeably better. It's actually pretty good reinforcement to see the positive affects of quitting. It lets you know that what you are doing by quitting is actually helping.
I know a lot of this seems contradicting to my attitude about my habit, but I have found it relatively easy to just stop and not even think about dip and these are the methods I use.
