If you don't finish, you know you'll get another chance next week. Any big things, like repairs, or erasing crayon from the walls, get added to a running list. When it is the day to clean that room, you try to accomplish the special project. This really helped me feel like I could keep up. Put your toddler to work.
Toddlers love to help and want to, too.
Accept all offers of help. If someone wasn't willing, they probably wouldn't have offered. Keep a sense of humor and of perspective. I have laughed and laughed at the sight of a room doused in baby powder. Also, our time with these little ones are so short-ask anyone with teens, they'll tell you.