Once I mix a song I like to take it home listen a bit and then take it for a spin on headphones on the way back to the studio in the morning. The one thing I have to do while doing this is to have something to write down every little gut feeling I have. If I forget one thing, I may miss it and it will haunt me forever. I am sure if you have made even one recording you have went through this too. This is why it is so important to always have something to write on when evaluating a recording of your song.
David Allen author of Getting Things Done goes into this theory a lot. He argues that your mind is the worst retention device and even those people with a great memory are going to forget some things. I could not agree more. What I have found is the best thing to do when listening to a mix or a demo is to make sure I can email, text, or write down any idea I have. Personally, I email myself all of the changes with the name of the record as the subject so it is easily searchable, even if I do mix changes months later. If you can’t email from your phone and it is all you have, you can text an organized band member with the idea and have them copy it down. Just don’t lost the idea what ever you do or you will be haunted by the ghost of song flaws past for all of eternity.