The same as get your shit together. Basically means calm down,
don't panic, or focus. Usually
said if you are normally good at something, but aren't able to do it well because your mind is preoccupied with something else, or you're just
tired.
Kevin: Get your head on
straight Amit, my grandmother could have gotten that rebound.
Amit: Sorry man, I'm still
tired from that
party last night.