Serena: But you guys are my two closest friends. Why couldn't you just tell me that?
Dan: I was hoping it would go away.
Blair: I was humiliated. Which is why we kissed.
Dan: To make sure nothing else was going on to complicate us or hurt you.
Serena: And?
Blair: Biggest regret of my life.
Dan: I mean that's a little bit of an overstatement, but yeah, it was not a good kiss.