How do you know when a familiar silence starts lying to you?

I've been guiding the same ridge for a decade and last week it felt wrong in a way I couldn't point to. No change in the rock, no weather shift, just a kind of watchfulness in me that wasn't there before. Have any of you had a place or a routine or a person you trusted completely, and then one morning the trust just quietly unseated itself? How do you tell the difference between your own mood and something real?