Don't worry, that's a common syndrome. You're not alone.
If you can't find someone to help you, try just either setting a time limit or a limit on the number of "test mixes" you will allow yourself to make. Make a game out of it: "How good of a mix can I make in three hours?"
As you get more experience and practice, you'll find a few things happening:
First, you come to have a better ear of just what *the tracks* in front of you are capable of, and that more often than not, what's causing your bouts of endless mixing probably isn't so much OCD (though it could be), or a lack of skills on your part (though it could be), but rather that you're simply trying to make the tracks do something thy don't want to do or sound like something they just can't sound like.
Second, you'll find that there's usually not much point in taking that much time on a mix, because one usually makes the best mixes - either by design or by chance - pretty early on and that one usually reaches a point of diminishing returns that makes further work too costly in time and effort for very small benefit.
Third, that it's far healthier to one's psyche, bottom line and skills development to just accept a mix for what it is and move on to the next mix, making improvements in the next process (hint: learning to get the tracking better) instead of trying to improve this one.