You know those little jam packets at the restaurant? I've found that one of them is too much for a half-slice of toast, too small for a full slice. So, I have three options: 1) use one packet for a whole slice and not get enough, 2) use two packets for a slice of toast and get too much, or 3) use just enough and waste some jam. I never choose 3). And, if I'm eating, say, a chicken dish of some kind and am full to bursting, I will continue, and if I simply cannot eat any more, I'll hunt through the dish for chicken chunks and eat them. I have even caught myself muttering, "If the chicken died for me, I can bloody well eat it all."
I'm wondering at the source of this. It could well be the left-over influence of my mother's "Children starving in Asia" ploy that she used as part of her "clean the plate." syndrome. Or, and I like this because it's the nobler, it could be that I am very aware of the dynamics of life and death. In order for me to live, something has to die -- fruit, chicken, lettuce, whatever. Our whole existence is built on the destruction of other things, from landforms to linguine.
This is not something to despair over, or to try to prevent. Every other species in the world does the same thing. Not only that, but the wind does it, the waves do it, the clouds do it.
There is no such thing as the "balance of nature." All there is is a flux of forces, building, tearing down, moving around, shifting, always shifting. Best to move with it.
And yet, I still can't waste half a packet of jam.