My Minecraft Launcher won't open minecraft.

I have a Mac. Maybe that's the problem. Maybe my account. But anyway, what happens is I open the launcher. Which works fine. I try all of my accounts and all versions, but when I click play, it opens game output (Insert account name here). I go to the launcher log and it always says:
[23:49:20 ERROR] Coudn't launch game
all other things seem to be fine. But go look at my account if you will or can. It's SkyyWoolf.