Pull my hair out! Instead of staring at the screen until my eyes go fuzzy, I tend to simply stop writing and do something unrelated. Going for a walk is great as it not only clears your head, but distresses you. Most of my ideas happen upon me unexpectedly while out walking.
Writer's block is a real pain in the ass, and the best thing to do with things that get to you is to ignore it. I take the same approach. If you think about something too much, the harder it will come to you. Back away and it will come.