How was your journey home yesterday?
Did you sit in your car, or on the train, going over the events of the day?
Going over and over the conversations you had - what you could have said, what you should have said.
When you got home, did it continue. Instead of inside your head, you went over things with who ever would listen, "you wouldn't believe the day I have had, and I should have done this and I could have done that..."
Do you remember how you were feeling when you replayed these incidents over and over in your head? Upset? Anxious? Angry?
You may have left work hours ago, but the replaying of your day is keeping those feelings alive...
The name for this is rumination.