Don't beat yourself up over it, try to learn what your state of mind was when you decided to pickup.
As for quitting for good, like Dee said many of us including me tried many times. Stopping for good sadly often requires hitting our own rock bottom. I had to realize that I was dying to quit for good.
But it also takes more than will power after detox. It takes some kind of support system adapted to our needs. Some only use SR, and people like me need some extra support in AA, AVRT, etc.
Hope your day 1 goes well and many more sober days!