#1 You should take 15-30 min. breaks for every 1 1/2-2 hours of working on music to not fatigue your ears. This will give your ears time to relax and start back up with your song with fresh ears.
#2 Do NOT listen to your song at full volume for long periods of time. You can and will damage your ears. Why would you want to damage the very main things that help you make music?
#3 Listen to your song around “conversation level” if not a bit louder while producing and mixing down your track. You can (and should) at times turn the main volume up to listen to the song at a loud volume as well as playing the song at a lower volume to see if any sounds are too loud or soft. i.e. You play the song at a lower level and notice the snare goes away or you turn up the song and you notice the kick is too bass heavy.
#4 I hate to say this one, but drinking inhibits you from hearing your mix as cleanly as you could sober. Your ears act like compressors themselves and when you drink it “loosens” up your ears and they let in more sound so your mix will sound muddy and loud when in fact it isn’t as bad as it seems. Try keeping the drinking to the composition part of your job 😉
#5 Take care of your ears and they will take care of you. When you get a cold or allergies do not blow your nose hard or suck air in hard through your nose to clear it. This will clog your ears quickly and can cause ear infections. Not to mention the clogging filters out frequencies so you are not hearing with the precision you need. Blow your nose gently and let it come out naturally. Sometimes your nose is just inflamed more then congested and other then medication there isn’t much you can do. If it is allergies I recommend trying to find an allergy med that doesn’t make you tired or wonky yet keeps your nose somewhat clear. (I won’t recommend any since I am not a Dr. and we are all different.)