An odd couple I know, but Severus is not really a pure-blood and the one person he hates most in the world (besides Sirius) is James. What would be more tragic than him being in love with his greatest enemy's girlfriend..whom he could not have? Plus the whole "Harry has his mother's eyes thing", Severus hates Harry but Harry has his mother's eyes...which is always a reflection of Lily. That sort of keeps her alive, even though Harry is not her at all. I love the whole irony of the idea!
~Lady Black~