Definition
used to advise someone not to expect something to happen soon, suggesting that it may take a very long time.
别期望了，不可能发生。
They said they would fix the machine soon, but don't hold your breath.
他们说会很快修好机器，但别抱太大希望。
He promised to help me move, but don't hold your breath about him being on time.
他答应帮我搬家，但别指望他会准时。
The government says they will address the traffic problem, but don't hold your breath for major changes.
政府说他们会解决交通问题，但别指望会有重大改变。