This keeps happening to me.
-I'll mix a song, compare it to reference mixes and I'll think it sounds great.
-But then I'll come back an hour later and realize the mix isn't even close to being good.
Does this happen to anybody else? How do I stop this from happening?
Yes indeed...this can be quite disheartening!
I very much like the previously suggested 1hr (tops) session work with breaks, I believe somewhere in the social science/education field studies show 50 minutes is a max time period for prolonged/physically complacent study/focus. Im sure that varies per individual and circumstance, such as food consumption, ext. life variables/conditions, but for an aspiring individual I definitely suggest keeping that perspective (that concentration has limits with needs for rejuvenation, novelty, and/or rest) enough to consistently track when mind/ear fatigue begins for you.
An additional thought which may further potentiate the previous idea: reserve brief attention for your playback volumes--- notice your preferred levels or tendencies for changing levels over any given session. A serious aid for avoiding ear-attenuation to frequency profiles, dynamc ranges, and context generalization can occur via listening and working at CRAZY lower volume. Blasting playback for any prolonged period of time absolutely accelerates the ear/fatigue concentration/blur issue previous posters are mentioning---the frequency familiarity builds, the inattention to detail/error undercuts decision making, the lost macro perspective takes over entirely. Low playback vol is great thing in general for product quality most specifically bc it helps perception of dynamic or fader volume changes, while also affording clarity and balancing of mid frequency track to track as well. Test this assumption/concept: listen to a familiar/preferable song on speakers quite loudly, then lower volume where you can speak at conversation level and hear yourself perfectly well....focus and notice what you hear in the track now. Here, you'll notice bass is the first thing to go with low volume, extreme treble and low mids are next most difficult to hear, and often mids/highmids are the lingering frequencies at these volumes. Extensive time mixing songs will learn you this plural-truth as mids/high mid resonance and balance consistently delineate individual tracks from one another, where as bass, low mids, treble work have largest impact on the mix as a whole when balance is pursued per track and for the song as a whole.
But anywooo like always a caveat to be offerred:
crank the volume occasionally to remember emotive impact of song, to accurately perceive ambiance in the track (verb), for bass/sub work, and for testing how the mix/master holds up when played through pegged (perhaps distorting) speakers.
Fight to gain perspective at all costs!
-MadHat