I agree with GrannyH. I think to quit successfully, you really have to have a genuine desire to do so. If the will isn't there, it will be extremely difficult to resist the temptation, especially when you are overly stressed or other challenging situations arise.
After many years of failed attempts at quitting, I was finally able to kick the smoking habit for good back in April of 2008. There were two major differences between my final quit and all of the other failed attempts. The first difference was that I did not actually plan to quit when I did. An unusual opportunity presented itself when I caught a cold that literally prevented me from smoking for a couple of weeks (not for lack of trying though). When I began to feel better, my first instinct was to reach for a cigarette but just before lighting it, I thought long and hard about how that would just begin the cycle all over again. I ended up holding that same cigarette in my hand for nearly 3 or 4 days but I never did light it.
The second and most important difference was that I suddenly had a very real desire to quit. I was tired of feeling like a slave to the cigarette so I simply made a conscious decision to control my cravings and give it up for good.
I'd be lying if I said that it was easy. The cravings were intense and didn't ease up for a long, long time. I still get a craving every now and then when I'm drinking or around friends who still smoke but time has made it much easier to resist those urges.
One thing I noticed about my quitting attempts is that every time I would set a quit date, I would smoke even more than usual in the days leading up to the scheduled date, quit for a few weeks or maybe even a few months and then somehow end up right back where I started. I knew I was serious about it when I made the decision to quit but didn't feel the need to talk myself into having a few more cigarettes or a few more days of smoking before making it official.
The best advice that I can give to those who are trying to quit smoking is to work on building up your desire to really let it go. You obviously already know all of the reasons why you should quit but reasons alone aren't enough; you have to want it for yourself. Find the will and the way will reveal itself.
Good luck to you, Diana, and to everyone else who is fighting the same battle!