I think you first need to sort out exactly why you dislike navigation or why you've stopped enjoying flying and hopefully that will show you what you need to do to get back to the positive.
Is it self-doubt? Can I do it? Is this the correct way of doing it?
Is it a new instructor?
Is your job's stress creeping into your hobby? Perhaps it's time to take a few no-pressure flights doing just what you love about flying and slow it down a bit on the lessons?
Personally, I hate not knowing what to do but at the same time, I love the challenge of learning new things. I'm not on nav yet but I think I would love the problem-solving aspect of it not for the problem part but for getting the correct answer and showing the "problem" who is boss!
Good luck!