trying to stop smoking

Why is it that one of the hardest things to do is to stop smoking? I’m 23 and I’ve been smoking for thirteen years and I’ve tried to stop about a million times but it’s to hard. I can only stop for about 3 hours but then I start again cause I can’t deal with the withdrawal symptoms especially the being moody and angry one. Cause then I take it out on other people and that’s not fair I’m even sitting here having a fag while I’m typing this. It’s also harder because I’ve got other people smoking around me then it makes me want one and what’s stupid is that I can’t even afford to smoke because I don’t have a job yet. That still doesn’t stop me from buying them though and even the nicorette chewing gum and patches don’t work and I’m taking all my moods out on my fiancé. But he doesn’t deserve that I think that’s one of the reasons why I go back to smoking aswell so that he doesn’t have me being angry with him or arguing with him. I don’t know of any other things that can help me stop. so if anyone has got any advice for me then that would be really appreciated. Cause I need to do something to help me stop and quick cause it is interfering with my health and I’m ill all the time with it so if anyone can help please leave a comment for me.