Well, the maxim is supposedly from the Roman general Drusus, a member of the imperial family (this is the Drusus who was the son, not the brother, of the Emperor Tiberius), as this particular Drusus decides to take advantage of a chance change of heart by mutinous Roman soldiers in Central Europe:
"Those things that chance had presented must be turned to wisdom"
(Quae casus obtulerat in sapientam vertenda).
Tacitus, Annals, Book I, Section XXVIII (my translation).
The Loeb translation by John Jackson says it better than I do: "Wisdom should reap where chance had sown." (By the way, translators, take note how inevitably dynamic a good translation, such as Jackson's, is. Translation is a challenging art, not mechanical duplication.)
Louis Pasteur expressed a similar idea in this way: "Chance favors the prepared mind."
As the philosopher Ortega y Gasset never tired of pointing out, our circumstance offers many opportunities. Living is choosing which one to exploit--in the best sense of the term--to create meaning for one's life and for the lives of others.
It is a simple idea, but then so many ignore it and thus incur a high opportunity cost.
(Image of works of Tacitus in public domain; image of Drusus Julius Caesar in Prado Museum, Madrid, under Creative Commons License)