At the moment I toss it on my compost pile but even that feels bad. I have the same problem, I have to buy a little more than I need because brain sometimes will stop eating if it can't find the thing. I try to keep to safe ingredients that I know I almost always like, or that don't perish quickly. I ...

... have a 'miracle ingredient' handy that can be added to anything and makes it easier for me to eat any old leftovers (for me it's mayonnaise, chili or soy sauce, mostard sometimes, or some sauce with garlic).

... have a standard way to prepare stuff. I always cook the same few recipes, have a standard list of stuff at home, easier to find out what I will eat and be stocked up for it.

... only permit myself one experimental buy per shopping trip to avoid collecting too many things I don't like.

... still create cheese and bread waste in great amounts. I am learning to make cheese and bread myself and it doesn't always work out yet. My equines get the bread, every slice left is dried and they get one in their morning bucket. The cheese is thrown on the compost and attracts the neighbours dogs and they are cute.

... have also chickens, and plan to get two pigs, to feed food and garden waste to - not a solution for the urban dweller of course but a nice and natural solution.