remembering

Why is it that whenever I'm trying to think of something I can't remember it: a song I really like and would like to purchase now, a book I'd like to read but the second I entered the library it vanished, what I'd like to get for Christmas or my birthday, which actually is today (although its 1am on what still feels like the 28th), and other things, like how to end a sentence with an actual strong point.