bite one's lip

I bit my own lips to keep from saying anything.

I bit my lips to keep from making a sound, but it didn't work.

She started to say something, but bit her lips to hold it back.

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.