Gigs you've missed because the artist(s) did something you didn't agree with and you thought it wise to make a statement by not seeing/listening to them
And now you regret it.
I missed Outkast at the Pinkpop festival in 2000(?) because they were supposed to play with a full band but all they had was a backing track. Dumbest plan ever, silly principled 16 year old that I was.