It has been said that "if" is one of the smallest words in the English language, but one of the most powerful and gut-wrenching. Think of the consequences of "if." The course of your life turns on "if," what you choose to do and what you choose not to do. This tiny two-letter conjunction and noun creates your life.
In the poem, Kipling illustrates all the traits necessary to become a great man and leader. However, the great majority of people would have trouble meeting a few of the requirements that Kipling outlines. It would be nearly impossible for all but the most enlightened to live by the rules Kipling ascribes.
That is where the title enters. If you can live by seemingly straightforward but difficult standards, you are assured greatness. However, "if" is no small undertaking. It requires enlightment and nonegocentricism, like all the great spiritual leaders.
The simple title stands in stark contrast to the demands Rudyard outlines.