Leftovers 1000% I can't imagine not. But I realize not everyone feels like this: my FIL would not - like even from a restaurant when he couldn't finish. Thankfully my DH is on board. My kids were good about it too. Typically we would have a night to just have leftovers and clean out the fridge (there wasn't necessarily enough of one dish for the whole family so we would wait a night or two so we had enough options for everyone). Now that it's just the two of us I usually only have to cook every other or third night
I often repurpose leftover grilled meat or fajita meat/taco meat to go on entree salads etc. other than that it generally stays the same meal.