Unfairness is real. Complaining about it is optional. You get to pick which one takes up your afternoon.

You get a limited number of hours in a day, and grievance is expensive. Something genuinely unfair happened, and how much of your afternoon it takes up is a separate decision from whether it was wrong. Naming it once is useful, because unspoken unfairness leaks into everything else. Rehearsing it all evening hands the situation a second helping of your life.

Give it a container: ten minutes, one conversation, a page in a notebook. When the container is full, move to something that belongs to you. The injustice is theirs, and the afternoon does not have to be.