That "worth keeping" question is the hardest part for me too. I have a basic rule about if I've used it in the past year (which I know isn't perfect). It just helps stop the overthinking.
Ever try the "maybe" box trick? Put anything you're unsure about in a sealed box with today's date on it. If you haven't needed to open it in six months, you can usually toss the whole box without looking. It takes the emotion out of the decision in the moment.