Loss or grief. Perhaps rage. Disappointment. Rock borrom with nowhere to go.

The good thing with rock bottom though is, that can be a new beginning, as for the others that can go on and on, and even build up to intolerable levels. But I'd venture to say even that has limits before shutting off or going numb, but that can then be worked with too. As opposed to plummeting without knowing when it'll stop. Perhaps the plummeting is as far as how strong of a moral or value of ours that's being tested or strained before it snaps and collapses.

I would say the hardest thing to cope with is a relationship of any kind that we refuse to give up on but we also sacrifice ourselves for it. Until it's all gone.