I think power quality has a lot to do with it. Sometimes my system sounds bad and Most of the times it is clean and crisp. Maybe justification for a power purifier.
Mood
Last night, listening before I went to bed, I was convinced there was something radically wrong with my system. Nothing sounded good. This morning I decided to play something I was sure would sound good. All of a sudden my mood picked up. Now everything I heard after that was reference sound quality.
I wonder if anyone else has had that kind of mood swing from one day to the next.