Bad days are not a character flaw. They are a system failure, and a system can have a fallback mode.
The three lines:
1. Drop to the floor: the minimum version of your routine, decided in advance. Not zero. Minimum.
2. One kind act toward your own body: water, real food, a shower, ten minutes outside.
3. No big decisions until tomorrow.
Write your three lines while today is still a good day. That is the whole trick. The protocol only works if it exists before you need it.
What is your floor? Comment the one thing that stays even on your worst day.