Interpret the keywords of the quote. For instance, I first looked at the definition of "modesty" which is:
"The quality or state of being unassuming or moderate in the estimation of one's abilities."
From this definition, you can tell that the term 'modesty' is a good trait; you behave well when cooperating with others. Now focus on the other two keywords/key phrases: "fool" and "man of sense".
"A person who acts unwisely or imprudently; a silly person."
Fool can also be determined as senseless. And obviously, a "Man of Sense" is the exact opposite. So this quote is saying that if a fool has the trait of modesty, people may look at him as a man of sense, someone to look up to, rather than a fool, which is someone you tend to ignore/not care about.