One of the housewife's great qualities was the art of using leftovers. Without throwing anything away, she knew how to incorporate leftovers from previous meals into new dishes. If it is "easy" to make a shepherd's pie with leftover meat, there are many other recipes that lend themselves to this game.
Some are so tasty that you wouldn't wait until you had leftovers to make them. Just reuse the day's leftovers!