My brain is a lot like my purse. There's a lot of useful stuff in there, most of it, however, meant for a specific situation. You just kind of reach in, grab something, and pray it's what you wanted.
For example:
I need my wallet. I reach in, grab something and pull it out. It's a shovel.[footnote]I swear I'm not making that up. It's one of those small collapsible shovels the military gives soldiers.[/footnote]
I'm taking a physics test, and need to remember a formula, but all I can think of is Star Wars trivia.