Hey, don't feel guilty! I know, it's not that straightforward... But keep reminding yourself that guilt serves no purpose than to keep the perfection/imperfection/guilt cycle going
You can break that cycle by teaching yourself to cut out the guilt part of the equation. Accept you won't get it perfect every time. Nobody does! If someone you loved skipped a workout, would you lay a guilt trip on them? Don't do it to yourself either.
This journey's basically a long series of moments where we have to do the best we can with what we have. Sometimes we hit the target, sometimes we miss. As long as we keep on shooting, we're already doing better than we were. Results come naturally from that. Let go of any negative thoughts, what's past is past, and just face your next eat/exercise decision with the best you can give it. And if you miss? Let it go and take a shot at the next target. And if you hit it? Feel proud, and remember that's proof that you CAN do it! Just not perfectly, all the time.