I'm kind of surprised that some people don't eat leftovers. While it's understandable from a taste perspective the time required to cooking fresh food every day, assuming you cook most meals, seems staggering.
I agree to focus most on the meat, mainly because it takes 10x the resources per pound to produce compared to vegetables, so it's the most valuable resource.
It gives me a warm feeling to hear advice like that being taken to heart. I would like to say that I always do the same, but I know that this will stick in my mind.
Anything spicy improves with a little time, and I've found the same to be true with tomato sauce and cooked cheese - so curries, chillies, lasagna etc etc all improve. soup is often better the next day too.
Using left overs is a way to cook more complex meals!
If you enjoy handling food then learning about handling left overs is a big part of that. If you go back and look at weekly food schedules from the past you will see patterns, were people cook one type of food day one to have base or ingredient for the next few days of cooking.
My comment was not so much about leftovers as it was about the time it takes to cook. And while I certainly do use the leftovers I end up with, I also try cook in such a way that it minimizes leftovers.