“Strike while the iron is hot.”
Meaning: Make use of the opportunity while you still have it; before you loose your chance.
The best time to shape iron is while it is still hot. If you wait for it to cool down, it will harden, and you will loose the chance to shape it the way you want to.
If you are at a networking event, and find yourself in a one-on-one conversation with the hiring manager of a company that you’ve always wanted to work for, deciding to tactfully sell yourself to that person, would be an example of striking the iron while it is hot. People who make a living off trading in the stock market, serve as great examples of the benefit of striking while the iron is hot.
This idiom can be used when giving advice to someone who is hesitant to take action, especially when the opportunity is rare, or when you’re having one of those motivational conversations with yourself.