Today we are having manicotti, lettuce salad, and garlic toast leftovers.
It makes a difference if you have facilities that will allow you to heat leftovers, microwave, toaster oven. If not you might need to invest in a wide mouth thermos for soups, stews, chili, casseroles, etc. Personally leftover are a no brainer for me. I literally package up the next days meal with leftovers and put them in the fridge. DH and I both have kitchens, with microwaves, that make this the easiest option.
I also keep salad ingredients on hand. I can either add a can of tuna, or some chopped meat, or an egg or too to top the salad. With a side of a roll or crackers it's easy too.
I make deassembled sandwiches too. I'll package the bread in a baggie. Then I can have another baggie for bacon and lettuce and another one for tomatoes. I can then make a fast BLT without anything getting soggy. Sometimes, I'll mayo the bread then add lettuce leaves to both pieces of bread then add a tuna salad or egg salad in the middle.
Sometimes homemade soup in a thermos and a side of muffin and a piece of fruit.
With the cold weather we've been having, I love having a hot meal. In the summer, I like cool meals of sandwiches, salads (lettuce, fruit, main dish, or desserts). I love sliced fruit, some might like that over cottage cheese or yogurt.
Good luck!