At a time i needed money, i sold my absolute favorite most meaningfull card that i owned, my 1952 Topps Mickey Mantle (PSA-2). I was miserable for many many years until i was finally able to replace it. But now i am happy because its been replaced by a virtually equal card (its only a PSA-1 but i love it).
I have learned my lesson though, and in the future, if i ever have to, i will sell my entire collection but keep that '52 Mantle.