Try something that takes you out of the regular gameplay. Make a homeless sim that only couch surfs and cooks at friends houses. If you have Outdoor Retreat, make a sim that only has a tent and survives by fishing, collecting and learning herbalism. Find something in the game that you don't usually do, and do it. Make over a Medieval Town with little shacks make over the residents to dress in old fashioned clothing. Demolish the health club and night club. Make all the sims go fishing and build wooden crafts. Or make over the town as a future city, replace all the houses with the futuristic houses from the gallery. Have your astronaut sim build rocket ships for a living.
If that doesn't work, take a break from the game for a couple weeks, or a month. Do something new in Real Life. Learn how to play the penny whistle. Go walking in a neighborhood you've never been to before.
