Ruminate

Focusing on past events in your life, typically ones that didn't turn out the way you would've wanted, and reflecting on them relentlessly with a strong outlook of yourself feeling worthless and inadequate. Depression and anxiety usually follows.

A very common negative thought process after breakups.

Jim: "The definition provided by Jack didn't get very many likes. It didn't even get a whole lot of views for that matter. Now Jack ruminates in the event with thoughts of failure and poor self-image."

James: "Jack looks like he has a lot on his mind."
Jane: "His girlfriend just dumped him. It was simple incompatibility reasons."
James: "Ouch, but why is he taking it so hard? They were only dating for two months."
Jane: "Jack spends a lot of time inside his own head with negative self-talk." He ruminates too much instead of using this as an opportunity to grow and improve."