Unrequited Passion

It's possible to love with passion for so long that you forget what it was that captivated you in the first place but you're unable to stop loving because the passion has acquired an impetus all its own that hurtles you onwards into spaces that only exist because the things in which you used to believe have disintegrated, leaving a gap that needs to be filled. The loved object becomes entirely irrelevant, other than in the theoretical sense of fuelling a distraction, of helping you forget - indeed, when all is said and done, of keeping you alive.

And no, you never or seldom get anything meaningful or encouraging back from the loved object, which if it had a personality and/or a will would almost certainly actively despise you anyway.