All of that was crushed when it became clear your ex wasn’t holding out for you at all.
Or maybe you didn’t even realize you were holding on to the fantasy until the moment your ex actually got with someone new. You know how deeply connected you once were with your ex, so knowing your ex is feeling that deep of a connection with someone else confirms the fact that you are no longer relevant.
If you weren’t broken up before, you sure as hell are now.
During your post-breakup period, it was easy to push your limits with your ex, whether it was with those drunken hookups, calling him or her late at night “just to talk,” laughing together at parties or joking about the silly or embarrassing things that happened in your relationship.
Back then, the two of you likely shared bonds that were unbreakable. Together, you forged ahead and made a relationship for yourselves. You shared great times and fun places together, and those memories will live on within your ex's own mind just as they live on within yours.