If you're up for starting a challenge, there's a whole heap of them listed on the Challenges board (specifically
this thread). I've played a Rags to Riches challenge and still have that save to come back to. The collection ones do get that little bit grindy and boring after a while.
But if you're really not feeling it, maybe take a small break and focus on either building for a while or a game that you're more in the mood for. Sometimes it's just not Sims time.
Hope you do find something that'll put a little excitement into the game for you.