Something that has come about me recently, is that I (usually when tired) seem to forget recent memories that my conscious deems "unimportant."
Today, for example. The last thing I remember, practicing piano and then poof - one and a half hours have passed and I am in my bed, being called for dinner. I think I just need more sleep, but today's one was really abrupt. I mean, I don't think I could've been that tired concentrating on playing in the middle of a song...