Just exactly what Jay said... record yourself every time & listen back to it the day after as you go about your daily shit - you get a much better appreciation of what worked & didn't, what to try more and less of and you get to know your tunes a lot better. While you're actually mixin you can't really get that perspective on it as you're more focused on the moment.

Also buy a stack of new tunes if you can, that always works...