I know what you mean. It's quite the paradox: your rational self tells you one thing and your emotional self tells you the exact opposite. It's the worst because you want to listen to your rational self but emotions take over instead.

Deep breaths help me sometimes. Watching a movie or reading to get my mind off of things can also help (although it can also exacerbate it if you feel like you're wasting time).

Hope you start feeling better soon! It'll pass...