Hi Amy!
I have this problem a lot too. It took about 2 months to get to a game in Sims 4 that I wanted to continue. I really enjoy legacies and "perfect" games - getting all unlockables, all skills, completing all aspirations - with aging off. Don't be afraid to change the way your game plays to focus on what you enjoy. Do you enjoy CAS? Something I enjoyed in The Sims 3 was sending random townies to CAS and giving them makeovers. How about your create families to populate your world, so you know them all? How about Build Mode? Then you could make a single Sim whose only goal is to make money, and work up to buying a mansion of your own creation. Do you like children, or teens, or maybe even ghosts?
Let us know how you get on and if you would like any more advice!