Thanks for your thoughtful review! I'm glad the story warmed you up on a cold day!
Yes, you're so right, it was a moment of realization for Harry as well, how quickly fortune can change, and what one took for granted could be lost in a heartbeat. He of course learnt this lesson on the night he killed Voldemort, but I think he saw it from a different perspective as he considered Snape's pitiful existence.