It sounds silly, perhaps, but I wonder if we really know how much money we throw away with the leftovers each week. I started making a concerted effort to use every bit of food that is in the fridge. Whether restaurant or home leftovers and I found I was stretching 4 more meals, at least, by either reheating or using them in another way. I think we take how much food we have for granted sometimes.
If you refuse to eat leftovers, then do your best to not cook more than you will eat or order more than you will eat. I found the appetizer menu is a great place for me to order from. With the size prepared by most restaurants, a salad or soup and an appetizer is plenty.