The only confession I have is that I won't heal DPS who pull trash mobs on purpose.
Let the tank do it. If you want to tank, play a tank.

I also won't heal other healers who spam Medica II and Regen in the two Main Scenario Quest dungeons. (if they ignore my advice not to do that).

Whenever I enter a dungeon I put the game on full screen. I also usually switch to a PT chat only channel. I have never (and will never) put my attention elsewhere while in a dungeon.