Lots of good advice and approaches. If I get to the point where I feel I've "lost" what I was going for or gotten away from what was making me dig a track, I will put it on the back burner and work on something else. Takes me out of the frustrated mindset and gets the creative juices flowing. When I go back I usually kill any effects and start bringing up the tracks one by one till it starts to groove again. John mentioned Mix Recall. Great tool for this since there may have been a cool effect or something that you may want to have back. All the best to you.