Is your diet making you wasteful?

Sometimes when I want a little something to eat I might have half of a 100 cal pack or half of a low sugar ice cream. When I am satisfied I usually don't save the other half simply because half an ice cream doesn't keep well and because its a pain in the butt to deal with the others. Wasteful. Money wise, trash wise, food wise. 

So what is more important? To reduce waste or waist?