It comforts us to think that pilots are always sane, stable people. They are NOT always. I know some personally and know how they are, and I have experienced behavior I found concerning more than once from them.
The worst was in the early 2000s' An LH pilot at FRA. Came storming into the gate absolutely FURIOUS and screaming at the gate crew. He even started punching walls and knocking over stancheons. Heads down jetway, yelling all the while with nobody but shocked passengers looking on, and then proceeds to "fly angry"...taxi was scary fast, dipping wings on the turns, us rolling like pax in a car. Braking hard enough to throw us forward during the taxi also. Seemed like we were flying fast too..fire walled take off even though the flight was short (likely less fuel) and only about half full, and a high rate, nose down descent with the spoilers up most the of the way down, and then another "dukes of hazzard" taxi experience to the gate.
It was scary.