I like some things for leftovers (lasagna, meatloaf, fried chicken (like revenge, best served cold), etc.) but I don't like serving the same thing for dinner two nights in a row, and my spouse absolutely refuses to brown-bag his lunch for work. (He has issues.) I will sometimes eat leftovers for lunch, but I am kind of picky about what I'll eat the next day.
So, like a responsible person who doesn't waste food, I try to avoid having leftovers of most things. It is not hard to figure out how much your family eats and cook only that amount. I will make extra rice/pasta/veggies sometimes because those are easy to recycle into a different dish. (Leftover steamed rice + veggies + one beaten egg = veggie fried rice for lunch). And sometimes I plan for leftovers -- I'll roast a whole chicken, we'll eat half of it, and I'll shred the rest and serve it the following night as filling for chicken tacos, or stir it into a casserole, or make soup (with stock from the bones and fatty bits).
I don't just throw food away, though. I find a way to recycle it, or make damn sure I'm not cooking more than we can eat. That's just ludicrous.