reset all of your knobs to default and start the mixing process over again.
I have been mixing a track for the past week and thought I was close to being finished when I realized it had no focus. I kept trying to add different machines for a lead sound only to discover I already had a lead but it was hanging out with the sub bass right in the middle of the mix. I added some width to it, and brought it up close where it became more of a focal point. This completely transformed the track and gave it new direction and inspiration.
So if you have an old track laying around that you just couldn't figure out why it didn't sound good when you finished it, try a remix.