There is a "what grinds my gears" in every forum, every 6th month or so, always 20+ pages long.
Yes we all get angry with stuff, but reading about it only adds to those feelings, and we all now that anger leads to hate, and hate leads to suffering..

So: What in 40k makes you happy?
I start!

¤ Finishing that last model in a squad late in the evening.. placing a newly complete and painted unit in front of me brings pure joy to my heart!
(then I carefully place them in the cabinet, and say good night. I love them all )
¤ Getting a new codex after years of waiting, never abandoning my beloved army just because it was outdated and hard wo win with.
¤ Reminding my opponent to shoot with a unit he forgot to shoot with, and then see him miss all his shots with them. Karma.

What in the WH40k hobby makes you happy?