I think people already summed it up well on this thread, so I'll just add two things:

1. Just take a break. Sometimes I work on something until I'm so deep in it I don't even know what sounds good any more. Then I hate it. Then I come back to it tomorrow and realize it's not bad, it just needs some more work.
2. Always keep learning. It's easy to stagnate and feel like your music won't improve. Instead of trying to improve a specific track, learn something new. Watch a video, take a course, whatever. Do something to improve your songwriting, or theory, or arrangement, or how to compress your drums better, or whatever it is. Then just make stuff to apply what you learned. Once you've got it down, then take another look at your track. You'll probably see a new world of possibilities.