Why are breakups so hard?

Even when you know it’s for the best and you know that no matter how hard you tried, you two are just incompatible. I hate that I had to hurt him to do what’s best for me. He told me “You got what you wanted. We’re not together” except that’s not that I wanted. Hearing that hurt. And I heard the hurt in his voice as well. I wanted to be with him but I knew it wasn’t going to work long term so I had to do what I had to do. I know there is someone better for me out there but right now it just hurts that we had to end things on such a bad note.
Why are breakups so hard?
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