The only advice I can give you is...
Keep trying.
I must have tried, literally hundreds, perhaps 1000s, of times, over the 25 years I smoked heavily. And occasionally those attempts worked for as long as six months or a year, only to restart again. I ended up in the hospital with about my 20th bad case of bronchitis, and when I quit that time it stuck for over a year.
Sometimes it would stick for days, sometimes weeks, sometimes hours. It's the second hardest thing I've ever had to do in life, and thought I'd never do it.
But then one time, it stuck. It's now been almost 10 years since I quit, and now the cravings are completely gone (that's one problem, the cravings will last for a few YEARS even after you quit).
So, just keep trying. If you really want to, you will. Don't give up. Don't ever give up.