Always so close, but there's always that one moment

I hate that I can go 2, 3, sometimes even 4 months with out picking at my face. I feel so good about myself, I feel like I'm finally over it but then almost out of no where I have a complete breakdown. I pick at perfectly fine pieces of skin and I know that I should stop but I have absolutely no control over my hands. When I finally do stop I feel depressed, like I let myself down and I'm so embarrassed I want to hide. I hate this. I was fine 30 minutes ago. Now, now I don't know.