What can you do on a day when you cannot get anything done?

Lower the definition of the day to something achievable rather than writing it off entirely, since writing it off tends to extend it. A workable minimum: get out of bed, open a window or step outside for light, drink water, eat something, and do one small task that takes under five minutes. Light exposure and eating in particular support the systems that make tomorrow easier. Avoid using the day to catch up on worry. If these days are becoming the majority rather than the exception, that shift is the signal to seek support.