T-Rex: I am a generous guy! If someone wants to go in front of me in traffic, I slow down and let them in.

T-Rex: But it's all an act!

T-Rex: I let someone cut in front of me for two reasons: because I figure this way it's more likely they'll do the same for me in the future, and because I recognize that it helps the traffic system as a whole. But this isn't generosity, it's greed! It's well-presented greed. It's me selfishly wanting to get around quickly SO BADLY that I'll sacrifice the short term for the long term.

Utahraptor: So you think you're not actually a good person!
T-Rex: I'm not!

T-Rex: I'll ask if you want the last piece of pie before I take it, but again: that's just me selfishly wanting friends and knowing that actually showing my greediness impedes that. Otherwise I'd be gobbling it like crazy!
Utahraptor: Well, even if it's an act, at least you're pretending! Tons of folks won't even do that.

T-Rex: That's true! And... and that means as long as they're still around, then I'm NOT the worst person ever! Oh my God, now I have a perfectly selfish reason to be thankful for all the jerks!
T-Rex: You're SUCH a good friend, Utahraptor!