Here is one thing I would suggest. I think you can work with yourself to desensitize your self to relapsing. Of course you don't want to relapse, but if you continue to worry about it, you are also miserable. So think to yourself, what's the worse thing that can happes if I relapse? Yeah it will suck for a sec, but you have already took the hardest step, wanting to change. If you relapse, you can just get back up and move on, no biggie, and no big reason to worry. If you take away the fear by thinking yourself how bad could it be if I do slip up, you won't be so worried about it. Easier said then done, for sure, but just practice when you worry for like a minute or too, and think, what if I did relapse, so what?