“I can’t say, but I’m working on making it right, Mum.”

This sentence sums up Severus's life. Ever since becoming an adult - in the deeper sense of the word 'adult' - he's done nothing else. Albeit in his own, very special way. That is what makes him a hero. (It does not make him a nice man, though. ;) But this is real life, not a hero's epic.)