To hold your breath is to stop breathing for a moment on purpose. Under water, past a bad smell, or waiting to see whether the ball goes in.
The possessive changes with the person — she held hers, they held theirs. Deliberately it is a physical act you can time with a stopwatch; involuntarily it is what a whole stadium does at once when the ball leaves the boot, and English treats the two as one thing. Don't hold your breath is the one to learn first, because it does not mean breathe: it means do not expect that to happen.
1phrasehold your breathTo stop breathing for a moment — on purpose, or because the tension has done it for you.
“Hold your breath and count slowly to ten.”
Practised in Common Word Pairs