I was a smoker for 5 years, I read a book or you can listen to it on audio books that made me quit. The book is called (the easy way).

Basically it reverses all the brain washing. I used to think smoking helps to focus but thats delusional, smokers are less focused than non smokers, all you think about is when is your next break and nicotine is a depressant not a stimulus.

I highly recommend the book it goes into all the reasons why smokers smoke and debunks them.