Kairosclerosis - From a Dictionary of Obscure Sorrows (I STRONGLY recommend this book)

kairosclerosis n. the moment you look around and realize that you’re currently happy—consciously trying to savor the feeling—which prompts your intellect to identify it, pick it apart, and put it in context, where it will slowly dissolve until it’s little more than an aftertaste. Ancient Greek καιρός (kairos), a sublime or opportune moment + σκλήρωσις (sklḗrōsis), hardening. Pronounced “kahy-roh-skluh-roh-sis.”