For it is the part of a wise man to resolve beforehand that whatever can happen to a brave man is to be endured with patience if it should happen. It is indeed a proof of altogether greater wisdom to act with such foresight as to prevent any such thing from happening; but it is a token of no less courage to bear it bravely if it should befall one.
[Est enim sapientis, quidquid homini accidere possit, id praemeditari ferendum modice esse, si evenerit. Majoris omnino est consilii providere ne quid tale accidat, animi non minoris fortiter ferre si evenerit.]
Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher
Philippics, No. 11, ch. 3 / sec. 7 (11.7) (late Feb AD 43) [tr. Yonge (1903)]
(Source)
(Source (Latin)). Alternate translations:For it is the part of a wise man to resolve beforehand that whatever can happen to a man should be borne calmly if it should befall him. It needs altogether great judgment to provide against such evil happening and no less courage to bear it with fortitude if it should befall.
[tr. Ker (1926)]It is the mark of a wise man ever to consider, reflect, that whatever may happen to him should be borne with patience. It is, however, a mark of greater wisdom to take every precaution against the occurrence of any thing unpleasant, of a reverse of fortune; but it is an indication of a mind in no wise inferior bravely and manfully to submit to any change of fortune, however unpleasant, untoward, unfavorable, unpropitious.
[Source]
This appears to the the source of the paraphrase: "To yield to occasion is the mark of a wise man."