Minecraft Survival is completely laggy.

My Survival mode is completelty lagging.
What I expected to happen was...:
For it to be working smoothly and properly, no glitches or problems.
What actually happened was...:
It move once every like, 10 seconds. I couldn't do anything because it was so slow!!
Steps to Reproduce:
1. Go on Minecraft
2. Create a world in Survival Mode
3. Hit "Play SElected World".
I don't really know how it happened. It just, did. And now it's lagging up my Creative Mode! WHYYYY!!