趁chèn热rè打dǎ铁tiě

Literal: use the heat, strike the iron
Figurative: To act promptly while things go your way; unlike 一鼓作气, it is about timing, not drive. Strike while the iron is hot.

Where does 趁热打铁 come from?

It does not come from a specific anecdote; the image comes from the forge. 趁 means "to take advantage of," 热 "heat" and 打铁 "to forge iron": the smith has to strike the metal while it is red-hot, because once it cools it will no longer take shape. Hence the figurative sense of not letting slip the moment when things are in your favor: a client's interest, a child's enthusiasm or the good mood after a meeting. The same image exists in other languages, as in the English "strike while the iron is hot."

How is 趁热打铁 used? Two examples

孩hái子zi刚gāng对duì钢gāng琴qín有yǒu了le兴xìng趣qù，我wǒ们men得děi趁chèn热rè打dǎ铁tiě，给gěi他tā报bào个ge班bān。
Our son has just taken an interest in the piano; we should strike while the iron is hot and sign him up for lessons.
客kè户hù对duì方fāng案àn挺tǐng满mǎn意yì，咱zán们men趁chèn热rè打dǎ铁tiě，明míng天tiān就jiù把bǎ合hé同tong签qiān了le吧ba。
The client is pretty happy with the proposal; let's make the most of it and get the contract signed tomorrow.

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