Not leating me start minecraft

Hello. I'm having a problem with the game. I open up minecraft launcher then press the play button. It starts loading up the game and opens the minecraft 1.7.9 window. After a few seconds the window closes and it opens up the launcher again. It doesn't want to go into the game. It just closes. I have a legit account, I paid for minecraft and it doesn't want to open up the game. Even after re-download the game. First time this happens to me. Please help!!