Lots of people here with more knowledge and experience than me.
For years and years and years I couldn't get past a day or two. Maybe a week or two here and there. I didn't think I'd ever be able to quit because I was battling back the cravings day in and day out. I thought that would be my life forever.
I now have seven weeks and I am amazed that the cravings (for now at least) have simply subsided. It took me a lot longer to adjust physically and psychologically than I thought but it gets better.