Try, try again. Repetition is the key to this poem: it's only by shoving his age in our faces at every possible turn that the speaker is able to slam home the point that he was pretty dumb when he was 21. Subtle? Not exactly. But if you've listened to the same commercials over and over, chances are you'll start to remember a company's slogan. In this case, repeating our speaker's age reinforces just how stubborn and unchanging he really is.