Eme and Juliet are both right on the money. Don't beat yourself up about it. If so, the only thing you will accomplish is convincing yourself that you're some kind of loser, or that you'll never be able to do it. Try and try again, as they say; practice, practice, practice, WIN!
Not to mention, you have chosen to tackle three of the toughest things people all over the world face today - weight loss, more exercise, and stopping smoking. These are the three things that everyone wishes they could do. If they were easy, it wouldn't even be an issue or a problem.
It just so happens that I'm battling the same exact things you are - which should be no surprise considering just about everyone is. But finally, I'm getting it done. After 17 years of chain smoking since I was 15 years old, I HAD to quit. I felt TERRIBLE. I couldn't get anything done. I was huffing and puffing if I walked up two flights of stairs; had NO energy at all; had a chronic cough, etc. Not to mention that my 40 year old uncle dropped dead of lung cancer within a year of being diagnosed. I tried EVERYTHING and nothing worked. Finally, with the urging and support of my husband, I quit smoking with nicotine gum. It was the only thing that worked. It's been almost a year and I still chew the hell out of it. I also have a friend who chews the gum like a mad woman, and she quit smoking 17 years ago! LOL For me, I had to quit drinking coffee and alcohol, get rid of all the triggers. So far, so good. Maybe you could try that.
At the same time, I had gained nearly 35 lbs in less than two years - depression, lack of exercise, chain smoking. When I quit smoking, I was so fearful that I would try to "get my fix" from eating that I went on a diet. I've never had to diet before or exercise because I waited tables for 10 years. Therefore, I would get all the exercise I needed at work. When I quit doing that, I blew up, and FAST! I tried eating better, but with my hectic lifestyle, couldn't. I finally got on Jenny Craig, and so far, without any exercise whatsoever, I've lost 20 lbs. It's taken a few months, but it's working and I'm losing. It's very convenient and anyone can do it.
Now, it's exercise, which I still can't motivate myself to do. I know I need to, but I totally hate it and can't get enthusiastic about it AT ALL! However, the more weight I lose from dieting, the more motivated I become, probably because I've already seen some progress and getting the results I want doesn't seem so daunting now that I've lost some weight.
I guess it is a step-by-step process, and it's a process with a lot of trial and error. If you're anything like me, if it's not easy and results aren't immediate, you get totally frustrated and quit. I'm SUPER impatient and want things like I want them, NOW! These are the two things that were the easiest and gave me the quickest results. And I have to say, I honestly don't think about cigarettes that much at all anymore, and I feel like I was born with a cigarette in my mouth!
But the good thing about it is that other good and healthy habits follow - like I quit drinking alcohol when I quit smoking. Not really on purpose, but because if I can't smoke when I drink, it's like, what's the point, you know? I simply don't enjoy it. Plus, I know that if I got drunk, I'd smoke. So it's sort of another positive that's come from quitting. And what's even more amazing is that my husband still smokes and I can be around it and it doesn't bother me that much. However, he quit smoking during that first, very difficult three months. After that, he started sneaking behind my back. The thing about quitting smoking, though, for me, was that I really HAD to quit. It was not an option anymore. Also, I chose a special day to quit, our first anniversary. For some reason knowing the day that I had my last cigarette helped me resist smoking another one when I wanted one. It was just one little extra silly thing that motivated me. Maybe you could try something like that. Like I told myself that, if I have this cigarette, I won't be able to truly say that that day was the last time I had one. Silly, I know, but it helped.
GOOD LUCK, and don't give up! You can do it no matter how many times you start and start over. Just pick yourself up, dust yourself off, and try again!