Avoid having leftovers, if possible. If you do have them, use them again.
Leftovers can very easily be used for other meals. There are no limits to your creativity. Here are a few examples: make fruit purées or smoothies with damaged fruit, make soups with leftover vegetables, turn old bread into breadcrumbs, make a sandwich with leftover fish or meat, or prepare a salad with leftover cooked potatoes, pasta or rice.
Here are some recipes to inspire you: