You could summarize this poem in one word by just saying "stoicism." That's sto-i-ciz-um. Stoicism was originally a philosophical movement that taught that true sages did not experience emotions like fear and anger, that the truly wise man would be impervious to misfortune. "If" is a poem all about this philosophy. The speaker tells his listener not to tell anybody when he loses all his money, not to give in to hate, not to allow his friends or enemies to hurt him, and so on. It is a poem that essentially says that it is only by being stoic (by having a "stiff upper lip") that a boy can become a man, and that a man can master the universe. Okay, so the poem is a little rigid, and maybe a little unrealistic at times, but the basic premise—that success is based on one's ability to master negative emotions and to maintain balance in one's life—rings only too true.
You got this. Stoicism is about being in complete control—of one's emotions, of one's feelings, and of just about anything else that might distract us from the tasks at hand.
Sheesh, stoicism is a difficult philosophy to adhere to. It is almost inhuman to expect people to not experience negative emotions when they lose things or when they're defeated.
Have you ever the heard the term "boy's club"? Yeah, well, this is a boy's poem. No women are in here—anywhere. Not a single one. This is a poem about manhood, about how to become and act like a "man." It is clearly spoken by a father (or father figure) to his son, and it celebrates typically masculine virtues (strength, for example). In this day and age, that might seem odd. Women can be strong, too, that's for sure. In Kipling's day, however, gender roles were, well, a little more segregated let's just say. While the poem does offer some good advice, it is kind of a problem that the advice really only applies to the fellas.
Something just isn't right about this poem. Whatever ideas it expresses are cheapened by the fact that they are limited to only men.
It's sad, but to be manly is to be unemotional. The speaker tells his listener that, to conquer the world and to be a man, he has to be able to "watch" crummy things happen and simply fix them, without "breathing" a word about it.
This poem isn't just how about how to be a stoic, about how to handle misfortune. It is also about misfortune itself, about defeat. Just think about all the different kinds of loss mentioned in this poem: money, the things one has dedicated one's life to, one's character. Defeat, loss—these are part of life, and there's simply no getting around that. The poem makes that very clear. The speaker, for example, doesn't bewail misfortune, or spout lines about how unfair life is, but rather makes us understand that this is just the way things are.
This poem really stresses the importance of not having a defeatist attitude. In fact, a defeatist attitude is the quickest way to not get possession of the earth and everything in it. So, turn that frown upside down, future world dominator dude.
Defeats don't have to be permanent. If this poem says one thing, it says that defeat can be overcome, that losses can be turned back into wins.
In a poem that was inspired by a major political event (the Jameson Raid, an attempt to colonize South Africa further) you'd think there would be more politics in there. Despite the fact that there isn't a lot of obvious political business going on, however, this really is a political poem—just think of that reference to kings, crowds, and common people, or the whole business about taking control of the earth. Whether it seems to be or not, "If" is a poem about all kinds of different political issues (leadership, control of land, gender roles, etc.).
Politics is all about striking out a middle course, being able to talk to kings and commoners and remaining immune to harm from one's friends and enemies.
This stuff is terrible advice for a politician. After all, their first job should be to communicate with their people, not bottle everything up inside in order to portray some invented ideal of how to act.