Take a Break from Music
After hours of listening to the same track over and over, your ears will probably get exhausted. You will begin to lose your ability to mix the track properly. Take a break from your mix if you can. Sleep on it, and come back to it a day or two later. I guarantee you will hear things or notice things you wouldn’t have before. There’s nothing that can help you mix a track quite like distancing yourself from it for a while.