The best approach from my experience would be to call this a day and go to sleep, unless you have to deliver a finished mix to someone in the morning. The morning usually is wiser.
If you really have to work now, ok. Are you able to save session and/or snapshot the settings? If you are, start again from the scratch; start from the vocals and build everything else very carefully around them, out of the way. If instrumentation clashes with the vocals (guitars usually do) don't be afraid to EQ frequencies out as heavily as needed.
Go easy on effects and processors. Tired ears are not the best judges.
Good luck,
Slabrock
