Before you skip, say the real reason out loud. If it sounds fine, skip. If it doesn’t, go.

Reasons that work silently often fall apart when spoken. Inside your head it is all vague tiredness and general unfairness; out loud it becomes a specific sentence you can judge, and some of those sentences sound perfectly reasonable while others sound like exactly what they are. Saying it is the whole test.

Next time you are about to miss something, say the actual reason to the empty room in one plain sentence. Then decide. Some days you genuinely need the rest, and that is a fine answer, but you will know which kind of day it is.