B.F.
I put leftovers in the freezer, even if it's just a small amount. I use them for my lunch (I'm a SAHM) or for the kid's snack time. Those small portions really come in handy sometimes.
Sometimes I also intentionally cook double the amount I need and freeze the rest for a dinner later. When I'm in a rush or don't feel like cooking I can get something from the freezer. Pasta sauces are great for that. They freeze well and they are inexpensive to make in the first place.