I'm not saying it again!

Ever have a giant wave of depression and have no idea why?  That happened to me today.  And it was weird.  Like out of nowhere I was depressed.  No, really, like I walked out of 4th, went down some stairs, and BAM!  I was depressed.  I really want to know wtf caused it, you know?  If imma be depressed I want to know what I'm depressed for.  Goshh, I keep saying depressed and It's angerizing me.  Huff! -.-