Just walk away, and let your mind clear. Sometimes, it'll take awhile, but you'll come back with fresh mind (and ideas) for your game.
In the meantime, pick up a different game, until you're ready to go back to Simming.
As an example, I play my 2005 Sid Meier's Pirates game, when I'm burned out on Sims! I also have my 1996 TITANIC: Adventure Out Of Time (though I have to use "DOSbox" to run it), and Left 4 Dead 2 also.
By the way, I also have Sims2 and Sims3, if I want a totally different Simming experience from Sims4. Though if I'm burnt out on Sims, I don't normally play with a different Sim series. :/