As a rule of thumb, I tell myself that it’s better to throw away food than to overeat. (Preparing just the right amount is even better, but more difficult.)
What about saving for the next day, composting or donating? As a former professional cook it burns me to see such a casual suggestion to waste food. I’ve worked for people who would weigh the food you swept up off the floor at the end of the day to illustrate waste.
For years I had been throwing the stem of the broccoli into the compost only to find out that it's not only edible but it's really tasty.
Then I hear that the leaves of radish is also edible, so that gets thrown into a stir-fry / omelette / stamppot / salad for another meal..