Nicole Scherzinger is people. When people say “Don’t hold your breath” they don’t literally mean “Don’t hold your breath”, unless you happen to be someone who is holding their breath and is about to suffocate as a result, in which case you probably should take the “Don’t hold your breath” advice literally and heed it immediately.
But, that highly serious situation aside, people normally mean it figuratively. It means that the particular event you’re waiting for is unlikely to happen, so you’d be ill advised to hold your breath while you wait for it.
"It'll be HOW much back to Cirencester?"
In the song Don’t Hold Your Breath, Nicole is conspicuously distressed. We can tell this from the fact she looks all natural rather than done up for a party, she keeps running her hands through her hair and pulling a blanket over head head in an “I’m all distressed” fashion, and it’s raining everywhere she goes, even in her bathroom.
The thing she’s advising you not to hold your breath for is her coming back to you. Because you did something bad to her. Like the Sheriff of Nottingham did a bad thing to the people of Loxley. And Mel Gibson did a bad thing to a female police officer. And Hosni Mubarak did a bad thing to the people of Egypt.
Bugger you, Mubarak
Maybe you burnt down Nicole Scherzinger’s village. Maybe Nicole Scherzinger was just trying to do her duty as a police officer and you went and called her lots of derogatory names. Maybe you held the country of Scherzingopia in political, social and economic stagnation for a prolonged period, heaping misery upon millions of innocent people. Truth be told, we’re not exactly sure what the bad thing was that you did to Nicole Scherzinger-tower-burger-what's-that-yes-the-meal-please-no-not-large-just-regular-and-Sprite-thanks-very-much, but it was clearly pretty bad. When it’s raining in the bathroom, you’ve caused some real upset.
Look at that overflowing sink, you bloody monster.