Wiktionary
strike while the iron is hot
prov. Take advantage of opportunity. vb. 1 (context literally metallurgy English) To strike a hot piece of metal, especially iron, with a mallet or other tool before it cools, while it is still hot enough to be shaped. 2 (context idiomatic English) To act on an opportunity promptly while favorable conditions exist; to avoid waiting.
Usage examples of "strike while the iron is hot".
You don't have much time, that's why they say you have to 'strike while the iron is hot.
I want to put my questions as soon as possible-to strike while the iron is hot, so to speak!