This made me recall a similar discussion I had with friends: what would power your Patronus? In my case, it would be the day I left the English department and moved over to the Journalism department at my university. For an entire year, one woman at my university-who was one of the heads of the department-made my life a living hell. The moment I discovered that I did not have to put up with that b*tch anymore made feel pure happiness.
After the transfer had been completed, I ran into the head of the journalism department, who stopped and congratulated me on my award for my review of Skyfall. You have to understand: back at the English department, no one would talk to you in the hallway, unless they had an ulterior motive. They avoided your gaze and summons and continued in their miserable routines.
Thus, the happiness - leaving the department and being congratulated by the head of the journalism one-was unrivaled. Hence, even in my darker moods - which occur more than I care to admit, thanks to the concussion-I summon the memory and expels the dark perspective that threatens to claim me.