make hay make good use of an opportunity while it lasts.

☞ This is a shortened version of the proverb make hay while the sun shines, which dates from the mid 16th century.

2013New Statesman The optimists can never be that most desirable of things, a meliorist, because every setback is necessarily a disaster. For the pessimist, it's simply a matter of shit happens, but until it does, make hay.