bite one's lip

I bit my own lips to keep from saying anything.

I bit my lip hard, trying to force them back.

She bit her lip and tried not to let me see.

She bit her lip and looked down at the floor.

She looked up at him, and bit her lower lip.

I bit my lip, trying to think of something to say.

He bit his lip and almost looked away from her.

She bit her lip, then turned and tried the door behind them.

She bit her lower lip and looked away from him.

She bit her lip but couldn't call the words back.