Try not to think about it to much. Brush your shoulders off and start again. I like to stay busy and try and be as creative as possible to avoid future relapses. Sadly it doesn't always work but there's no point beating yourself up to much about it.
Well, I know I would always immediately go to YouTube or Netflix or eat something right after to try to distract myself from the guilt I'd feel right after. My therapist suggested actually not doing these kinds of activities immediately after in the interest of recording my thoughts about it. Makes sense. There does seem like there'd be value from "working through" those feelings and thoughts of frustration and remorse.