So I [...] devised a new ritual based on new principles. I kept that ritual burning in my mind for years, perfecting it in imagination, pondering its meaning and making fine adjustments, waiting for the intention to stabilise. At last I dared to invoke my ritual, an invented sacrificial ritual, based on a principle untested by all known magic. And I lived, and yet live." The Defense Professor spoke with quiet triumph, as though the act itself was so great that no words could ever do it justice. "I still use the word 'horcrux', but only from sentiment. It is a new thing entirely, the greatest of all my creations."

Rituals require sacrifice. Conceivably, Riddle sacrificed his ability to love, or to care about others.