That's what Angel's trying to escape in Reprise. That's what Buffy thinks her friends can't handle in Once More, With Feeling. Both of them take comfort in sex with a vampire.
Angel gets his moment of clarity after sleeping with Darla, but it doesn't last. He starts hoping and then he pins his hopes on family - primarily Cordy and then Connor, secondly on Wes, and then also on Gunn, Fred, and Lorne.
One by one, he starts losing what he loves. He starts losing his hope and his heart is bleeding out because of the pain it feels. In the end, he feels like he has to cut out his heart to continue the fight.
Just to compile some of the pertinent ideas:
"If we don't gut ourselves and burn out everything inside that gave her power over us, then we're lost." From Angel. The one who believes that not everyone can be saved. Who thinks that he's damned to hell.
"That the world we're fighting for? The right to be heartless, an uncaring shell? To be dead inside? That's not enough." And that's from Fred, who still believes. Fred hopes.
To be heartless. That's something that Angel would welcome. Hearts get in the way, right?
Love is sacrifice. Sending your lover to hell to save the world. Jumping into a portal to save your sister. Slicing into your son to save him. Giving up your chance at humanity to save a new friend.
What is right? What is good?
Are they always the same?
There's an essay about Terry Pratchett's books called
In Defense of Niceness that mentions the differences between Right and Good and Nice.
Excerpts that apply:
"Of Carrot, for example, Terry has said that he is "Good, but not necessarily Right or Nice". An understanding of the semantic scope of these words, of where boundaries between Rightness, Goodness and Niceness lie, casts light on the function of the various characters within the moral scheme of the Discworld. It is a notable feature of Terry's strong "good" characters that they have the potential to be evil, whereas the evil characters have no such potential for good, and this to a large extent accounts for the much greater fascination that the good characters exert."
"The perfectly good character would be right and good and nice (Brutha springs to mind), but the majority of good central characters embody only two virtues."
"Right is thus clearly the category into which the Patrician falls. He is perfectly willing to sacrifice individuals for the good of the whole, but he does his best to ensure that the price is paid by the smallest number."
"And in this sense, as a fully-fledged member of a community, Sam Vimes is undoubtedly Nice. He deals with his fallible fellow creatures on a personal level: he acknowledges their limitations, indeed hates them at times, but he knows them. Not in the manipulative, impersonal manner of the Patrician, nor in the idealising, impersonal manner of Carrot, but as a fellow-member of that community."
Who in the BtVS/AtSverse is Right? Who is Good? Who is Nice?