Explanations

The girl and the man were very close, though in truth she was not so much a girl as a woman. They must have been in love once, but the man watched as the woman slowly dissolved into a listless wreck from the strong, optimistic girl she'd once been. There was nothing to do to help, he thought, and he'd distanced himself from her to try to avoid her fate.

He regrets that now.

He thought that it would be better for one of them to survive, and that his involvement would doom them both. He wasn't wrong on the latter, but the former was extremely incorrect. He was involved anyway, and when They are concerned, death is preferable to the alternative.

The alternative, unfortunately, is what has become of the man, and no matter how much he wishes for death, it will not come for him until it is too late.