As a mastering engineer full time, meaning almost 7 days a week, this is a topic I know well ! When we sleep, out hearing recovers and in the morning things will sound different than they did at night. I think of my hearing like an hourglass full of sand. In the morning it’s as full as it can be based on the quality of sleep. As the day goes on the sand falls down, acerbated by a concert, or car window open, and eventually it’s all out, can no longer listen. Alcohol, sugar, stress, all factor into it also. In fact, just the presence of daylight vs dim night light will change our perception.
I prefer to do new work at night, and analytical fixes in the day. Others differ.
So yes our hearing is a moving target, yet in a range, and the more we know it, the better our perceptions. Listening daily with refs we know well for decades is the way to test ourselves. And of course, listen with the WHOLE body. Let the vibrations hit you head to toe. Bodies remember things like smells and tastes and sounds better than brains alone. Enjoy your listening !