I remember reading about a study indicating that thinking about what isn't here causes unhappiness (and vice-versa, we're generally happy “in the moment”). Rem

I remember reading about a study indicating that thinking about what isn't here causes unhappiness (and vice-versa, we're generally happy “in the moment”). Remembering good things (and apparently the past tends to be seen in positive light, regardless of whether we felt happy at the moment) causes the mismatch between our memories and the reality. Possibly because we're very social species, a deceased person causes the worst pain.