It's not a tangible emotion where you can grasp it and hold on to it. It's something without shape or contour or even substance, like a fog of negative space.
You question your worth, or rather, your meaning. For no reason at all, seemingly, you change from one day being someone's ice cream to the next day being that someone's porridge. Not bad or hateful. Just an unnecessary drudgery.
Yet you know at the same time that it's very likely that after awhile, this same disinterested person will probably switch on their interest again, after other, more interesting stimuli have been removed, or when specific occasions arise wherein it would be preferable to be interested in you.
Makes you wonder what's real, I guess. Makes you wonder if some of the things you took for fact were actually delusions, and makes you wonder if you really have the right to expect some of the things that you find yourself to have expected.
It makes you lonely--not only because someone who was there for you, spiritually, is no longer there, but also because the possibility that it was never anything real to begin with, occurs to you.
At the same time you're feeling like an old toy that has been put aside as interest passes, you begin to look at everything in your life as merely toys, with no more meaning than that, the pleasures they arouse no more than fleeting, temporary fancies. And because you want something that lasts, and everything looks impermanent, you wonder what the point is with dealing with these toys any longer.
How can you possibly enjoy them again?
Maybe the horrifying thing is that you in fact do.