What helps me is play what you have written so far. Not to see if you made any mistakes, but pure for the fun of it. Helps you remind what it is you created (and why). Get into the world you made.
You could also try to tell yourself what your game/world is all about. Just in your head (or out loud when your alone so people will think you’re not that odd). I do that sometimes when I am driving to work / school. Also, swimming helps. (so basically, do something that takes little though to do so your mind can wander, and no, I haven’t killed anyone while driving nor have I drowned).
Last thing you could do is just write a few lines that will come later on. Just write for a little while pure for the fun of it.