A setback costs you time. Letting it make you bitter costs you way more.

A setback takes a fixed amount from you: some weeks, some money, a season. Bitterness has no fixed price. It keeps charging after the original thing has finished, and it changes how you treat people who had nothing to do with it. That second cost is the one people fail to notice until it has been running a while.

Notice whether you tell the story more often than you do anything about it. Set a limit on how often it comes up, then let it be history. If you are still angry at one specific person, decide what you want from them, and if the answer is nothing, stop paying.