You have to get mad. That's what did it for me.
We were out riding our motorcycles one day (some friends and I) and stopped to gas up at the top of the Cherohala Skyway. I asked for a pack of Marlboro and the lady said, "5 dollars and 18 cents".
Instantly, I had a flashback to 1986 when it hit 1 dollar a pack. I remembered thinking, "this is bullshit".
Then it hit 2 dollars.
Then 3.
Then 4.
Each major milestone I kept shaking my head saying I should quit. When that woman said, "5 dollars and 18 cents" that was it. I snapped.
I told her, "Keep 'em."
I threw my lighter in the trash can just outside the door and never touched another one. That was 9 years ago. Good thing too...2 years after I quit is when they found the cancer.
Just set yourself a milestone, man. Do some mental inventory and determine your breaking point and when it gets there, get pissed as hell. It's still harder than hell, but anger goes a long way to quitting. You get pissed off enough it becomes personal. When you get to that stage, you WILL win.