There are companies I dislike, companies I disagree with, even companies that have occasionally angered me with disappointing gadgets that underdeliver. But to date there’s only one company that I hold a genuine, deep-rooted grudge against. It’s the reason I don’t have copies of most of the work I did in college, and…

We humans are masters of resentment—a characteristic that can be traced back the beginnings of recorded history. Feuds seem to be an indelible aspect of the human condition, but why should this be? We spoke to the experts to find out why we love to hold a grudge, and the importance of letting go.