Playing but game crashes

I can't play in my Singleplayer world

What I expected to happen was...:
i thought i could play in my world but no the game won't let me.

What actually happened was...:
I log into my world and i can move around for 1-2 min and then the game crashes.

Steps to Reproduce:
1. Get the game to run smooth like butter with Shaders on.
2. Get the game enable to say whats wrong.