You don't have to mix to be mixing
I got a lot of mixing done today, and I hardly touched a thing.
To me, mixing is a lot like sewing. When you sew, most of your time is spent getting prepped or cleaning up the project. Hardly any time is spent at the machine by comparison. You've got to measure, cut, fold, press, organize, triple check everything, and probably more I don't know about (I'm self taught by trial and error.)
Mixing is listening, comparing, referencing, note taking, etc. The tweaking of dials is the same thing as sitting at the sewing machine, the process is only effective because of everything else that goes on around the project.
I've read a lot of stuff on how to listen and compare, how to find references, how to choose which things to adjust, but I've hardly read about note taking.
Note taking starts before the song is even done recording. Stuff like goals and ideas. Things you'll probably forget way down the line when you actually get to the mix.
Note taking continues as you work on a song, listening back and writing down thoughts, keeping track of the current state of the thing and the thought processes behind the decisions.
And it really comes into force when you're analyzing the album as a whole.
I have a lot of good notes, some that have saved my skin, but I'm always improving on my notes.
One quick tip
Listen to The Thing, write down all the good notes you can, then take a break for a couple days. When you come back to The Thing, don't look at your previous notes until you've listened again and written a second batch of notes. Comparing the two sets of notes will result in a ton of clarity.