Say farewell to luck when winning: it is the way of the gamblers of reputation: quite as important as a gallant advance is a well-planned retreat, wherefore lock up your winnings when they are enough, or when great.

[Saberse dejar ganando con la fortuna. Es de tahúres de reputación. Tanto importa una bella retirada como una bizarra acometida; un poner en cobro las hazañas cuando fueren bastantes, cuando muchas.]

Baltasar Gracián y Morales (1601-1658) Spanish Jesuit priest, writer, philosopher

The Art of Worldly Wisdom [Oráculo Manual y Arte de Prudencia], § 38 (1647) [tr. Fischer (1937)]
    (Source)

(Source (Spanish)). Alternate translations:

To be moderate in good fortune is the part of a good Gamester, when Reputation lies at stake. A brave Retreat is as great as a brave Enterprise. When one hath acted great exploits, he ought to secure the glory of them, by drawing off in time.
[Flesher ed. (1685)]

Leave off the game with fortune while you are in luck. -- That is what all the best players do. A fine retreat is worth just as much as a gallant attack. Let a man bring his deeds, when there are a great many and enough of them into safety.
[tr. Duff (1877)]

Leave your Luck while Winning. All the best players do it. A fine retreat is as good as a gallant attack. Bring your exploits under cover when there are enough, or even when there are many of them.
[tr. Jacobs (1892)]

Quit while you're ahead. All the best gamblers do. A fine retreat matters as much as a stylish attack. As soon as they are enough -- even when they are many -- cash in your deeds.
[tr. Maurer (1992)]