Are you referring to your ability to feel engaged by the playing and the music? A lack of inspiration to move beyond your current state, whatever it is, as a player? An existential angst, a 'sameness' to it all that kind of stifles your muse?
If so, I think I know what you are talking about. Experienced it early after a few exciting years at the beginning of my so-called playing career. Started strong, hit a wall (probably of my own making), came back many years later, and cursed every moment I spent away.
My personal epiphany was the realization that in every endeavor, regardless of how low-brow or high-minded, your biggest gains are always as a beginner, because you go from not having any understanding at all to being functional and dynamic.
After that, the desire to keep going, stay engaged, and expand into new levels of comprehension are a matter of personal fortitude. If you don't really wanna, and it's not something you miss when you're away from it, it's only going to reach a particular level and stay there. IMHO, it is more constructive to plod along than it is to resume after completely stopping. You lose all kinds of important intangibles when you lay idle.
As a famous baseball manager once said, it's what you learn after you know it all that matters.
My advice is to tough it out, keep pushing, and reclaim that mojo. Unless of course, it truly doesn't matter to you and you have made the very personal (and sad) decision that this is the end of the line for you.
If this is the case, I have only one more question: What do you have to sell?
