Smiling is mostly about smiling more.

“Oh, Peeta, Don't make me sorry I restarted your heart.”

“Hey, Finnick, come on in! We figured out how to make you pretty again!”

“If you'd been taken by the Capital and hijacked and then tried to kill Peeta, i…”

“What am I going to do? I take a deep breath. My arms rise slightly—as if recall…”