Human intelligence could be defined as the capacity to learn from experience and adapt to new circumstances. In Principles of Politeness, and of Knowing the World, written in 1786, Lord Chesterfield provides us a wealth of advice, based on his own experience, so that we might excel in new circumstances that we encounter socially. Here is his description of modesty in social situations:
Forwardness being the very reverse of modesty, follow rather than lead the company ; that is, join in discourse upon subjects, rather than start one of your own: of you have parts, you will have opportunities enough of showing them on every topic of conversation, and if you have none, it is better to expose yourself upon a subject of other people's than of your own.
But, be particularly careful not to speak of yourself, if you can help it. An impudent fellow lugs in abruptly upon all occasions, and is ever the hero of his own story. Others will color their arrogance with, “It may seem strange, indeed, that I should talk in this manner of myself ; it is what I by no means like, and should never do, if I had not been cruelly and unjustly accused ; but when my character is attacked, it is a justice I owe to myself, to defend it.” This veil is too thin not to be seen through on the first inspection.
Others again, with more art, will “modestly” boast of all the principal virtues, by calling those virtues weaknesses, and saying, they are so unfortunate as to fall into weakness. “I cannot see persons suffer,” says one of this cast, “without relieving them; though my circumstances are very unable to afford it.” “I cannot avoid speaking the truth, though it is often very imprudent,” and so on.
Lord Chesterfield reminds us not to be forward or boastful in conversation. He suggests instead that we join existing conversations in order to seamlessly blend into our interactions, rather than forging ahead with new ones. If we have talents, they'll naturally shine, without help. It's better to speak on topics initiated by others than to draw attention to ourselves.
The worst kind of self-promotion, says Chesterfield, is the kind that is disguised as self-defense or self-deprecation. Such attempts are always transparent, particularly the "modest boasting" variety (or what we now call "humble bragging"), where individuals subtly flaunt their virtues by presenting them as weaknesses. This advice was relevant in the 18th century, and it remains so today. There is something about human nature that compels us to feel competitive in social settings, even when the stakes seem low. But real personal qualities are self-evident; they require no announcement or insistence. Take Chesterfield's advice: go with the flow of conversation, and let your accomplishments and virtues become apparent on their own.