What will your happiness hinge on? We can't know, Liz. There are no guarantees.
Have you been trying to be happier in this relationship because it looks so good on paper you would feel foolish if you let it go? Do you think it is what you are supposed to do or be? Do you wish you could appreciate it more, in your deepest heart?
If your answer to those questions is yes, then you have to at least consider the possibility that no matter how good a prospective partner is, you might not be able to embrace a relationship with them until you get right with yourself.
I'm celebrating my seventh anniversary today with my husband. We had mutual friends for more than ten years before we met, and we often joke about why the heck did no one introduce us to each other before?!?!? But the truth is, and we both know this, that as compatible as we are, as in love as we are, and as much as we respect and trust one another for the long haul, if we had met even as little as one year before we did, our relationship would have been a disaster, because neither one of us was ready.
Sometimes the timing isn't right. Until I learned to be okay with myself on my own, whether or not anyone ever came along again, the timing was never going to be right.