discretion is the better part of valor
In Shakespeare’s Henry IV, Part I when Prince Hal finds the cowardly Falstaff pretending to be dead on the battlefield, the prince assumes he has been killed. After the prince leaves the stage, Falstaff rationalizes “The better part of Valour, is Discretion; in the which better part, I haue saued my life” (spelling and punctuation from the First Folio, Act 5, Scene 3, lines 3085–3086).
Falstaff is saying that the best part of courage is caution, which we are to take as a joke. Truly courageous people may be cautious, but caution is not the most important characteristic of courage.
This passage is loosely alluded to in the saying “discretion is the better part of valor,” which is usually taken to mean that caution is better than rash courage or that discretion is the best kind of courage. Only Shakespeare scholars are likely to be annoyed by this usage.
However, those who take “discretion” in this context to mean the quality of being discreet—cautiously quiet—are more likely to annoy their readers.
Much more of a problem are misspellings like “descretion,” “disgression,” “digression,” and “desecration.” Unless you are deliberately punning, stick with “discretion.”
The Week's End Extra from the Archives: "How to verify standard English usage: an explicit guide" (December 11, 2012).