In this poem, Kipling's speaker outlines for his son the behaviors and attitudes it takes to become a man—in this case, a gentleman in British society. It is good to keep in mind, however, a concept from the Italian Renaissance that lies behind the speaker's advice. This is sprezzatura, which means projecting a nonchalance or effortlessness in everything one does, and in that way, making difficult tasks look easy and natural.
In the first stanza of the poem, the speaker advises his son to cultivate keeping his cool or keeping chill when others around him are losing it. He also advises his son not to repay low behavior with low behavior—don't respond to lies with lies or hate with hate. In other words, to use current parlance, when others go low, you should go high. He advises sprezzatura, too, when he states his son should make this all look natural and effortless:
yet don’t look too good, nor talk too wise
In the second stanza, the speaker turns to advising his son to develop self control, as well as an ability to hear the truth and avoid flattery and have grace under pressure. No matter what happens, his son should respond to it with cool equanimity, treating triumph and disaster with the same ease. If his life's work is broken, he should simply quietly and graciously pick up the pieces and rebuild, as if it is costing him no effort:
watch the things you gave your life to, broken,
And stoop and build ’em up with worn-out tools
In the third stanza, the speaker tells his son he needs to develop nerve as well as grace under pressure. He describes this as follows:
If you can make one heap of all your winnings
And risk it on one turn of pitch-and-toss,
And lose, and start again at your beginnings
And never breathe a word about your loss
It's nervy to bet everything on one toss—but the important thing is to keep chill no matter what happens. Never complain or show your pain. Always maintain the stiff upper lip.
In the final stanza, the speaker tells his son he should treat all people, whether kings or commoners, with the same courtesy, and that moreover, he should stay aloof, never getting too close to anyone, so that
neither foes nor loving friends can hurt you
At this point, if he can do all of this, his son will "be a Man."