Why does any small slip up on my diet or sleep etc. cause a chain reaction where everything becomes terrible?

That is because you are unforgiving of your mistakes. That is because you expect such perfection from yourself that even a tiny mistake would trigger a chain reaction. You need to realise that you are only human; and the beauty of being human is allowing yourself to slip up, because it is because of those very slip ups that you learn to be stronger, braver, and more resilient. It is okay make mistakes. It is okay if you're not following a routine 100%. And coming to terms with yourself, your mistakes and acknowledging that you are bound to make slip ups in order to grow is part of the deal, will help you stop the chain reaction from triggering.

That's a really good question! I struggle with that a lot myself, and I feel like there's no easy answer. What I've personally found is that normally slipping up on something like that just sets you off balance, and it's a lot harder to get back on track again. Thankfully, it doesn't have to end in a terrible chain reaction. I've personally been working really hard on recognizing those slip-ups as early as I can, and I've found when I correct them right away, the chain reaction normally isn't quite as disastrous. That's easier said than done though, and for me, staying accountable someone close to me (which could be a person I see in person a lot or a listener on 7Cups!) who regularly checks in, and who knows what things tend to send me down that dark path, can make a huge difference.