Today

Freezing leftovers is a great option! I have learned to ALWAYS label the container lids. I use some left over name tags and each time I reuse the lid I cross off the last item and add the new one. Uses the labels which otherwise are going to waste, uses them multiple times, and they may or may not come off in the dishwashing process. Leftovers this way really can be rotated so no one gets tired of any one item. It also means I can purposefully make large batches of items that can be pulled out when I don't have time to cook a new meal. Of course, salad is not one of the things I put in the freezer! :-)

never thought of that

I use leftovers for lunch the next day.

We rarely throw anything out. We either eat the leftovers as is, make sandwiches with them, make soups, add them to salads, or add other ingredients, and make something entirely different.
Once I heard about chefs who were asked what they would ask for if they knew it would be their last meal. Most did not choose the foods they were famous for, but instead the homey foods that they grew up with. I thought about this and decided that I would choose leftovers for my last meal. I always enjoy the possibilities they present.