My Minecraft is not launching!!!

Hi. I could play Minecraft 2 days ago, but right now, I can't. I would open Minecraft and it will show the minecraft launcher, as usual, but after I hit the 'Play' button to play Minecraft, it will show me the launcher again. I tried it over and over again! I closed my Minecraft, restarted my Windows 8, I tried for 2 days and my Minecraft still doesn't work. Please help me. ( 1.8.9 )