That's a Bummer
The Italian Stallion sounds like a Kentucky Derby-winning horse, but it's the nickname of Rocky Balboa, a.k.a. our protagonist, a.k.a. the contender for the heavyweight title.
But before he's a contender, Rocky Balboa is a bum. He boxes with bums as a hobby. He makes very little money boxing (winning a fight nets him only forty bucks), so he has a job with a loan shark as the muscle who shakes down bums. And he can't get a date… because he's a bum.
And this bum-ditude bums him out. He feels like his youth and potential is slipping away, and that he'll have gone to seed without having ever bloomed:
ROCKY: Talkin' about your prime. What about my prime, Mick? At least you had a prime. I ain't had no prime! I ain't had nothin'!
Of course, he gets a ton of negative reinforcement. Mickey even tells him, "Nothin' special about you." And hearing that, as you can imagine, does wonders for a man's self esteem.
Rocky may be a bum and a shady loan collector, but he's a sketchy no-goodnik with a heart of gold. He's a sensitive man who keeps a goldfish named Moby Dick and two turtles named Cuff and Link. (Aww. That's just adorable.) And Rocky wants to find true love even more than he wants to be a boxing machine.
And we're not just talking about hearts-and-flowers love. Rocky wants to love himself and he wants to love someone else. Having self-esteem and loving another person are both unfamiliar feelings for poor ol' Rocky. Mickey constantly berates him and even takes his locker away, which leads to Rocky being as adorkably awkward around Adrian as a middle schooler on his first date.
The term "manchild" is often used as an insult, but Rocky's childlike sweetness, coupled with his burly physique, makes him totally endearing.
Rocky's personal life is rough around the edges, and so is his fighting style. Mickey tells Rocky, "You got heart, but you fight like a goddamn ape." Our little Magilla Gorilla can't spell finesse and he doesn't have any in the ring. Part of the reason why is because he's a southpaw, or a leftie. Apollo's coach, Duke, tells Apollo, "I don't want you messin' with southpaws. They do everything backwards." That line could apply to Rocky's life as a whole, because he always feels like a bass-ackwards screw-up.
But we can't just blame Rocky's lack of grace on the fact that he has to use left-handed scissors. He also has a hard time smoothing out his edges because he's… vain. Yup. He's proud that he's never broken his nose, which is kind of like being a prima ballerina and being proud that you've never crushed a toenail in your pointe shoes, or being a writer and being proud that you've never worn reading glasses or succumbed to a crippling Red-Vines-and-black-coffee diet. Getting your nose broken is part of the whole boxer steez.
Also, he never takes advice from coaches. He's stubborn and has a real "my way or the highway" ethos, which makes him a true American icon, but also makes him a lesser boxer. Lucky for us (and Rocky), he learns to swallow him pride right around the time that his ego gets an Adrian's-love-fueled injection.
Coincidence? Not even close.
In the title fight with Apollo, Rocky manages to go the distance because he finally swallows his pride. He takes Mickey's advice, and he doesn't worry about his precious nose. In fact, it gets broken in the process. But by breaking his own nose, Rocky mends his spirit.
Just Do It
Aside from the smashed schnoz, Rocky doesn't change much during the movie. He succeeds first by catching a lucky break, and then by tapping into the personal drive that he's always had, but has never had to use. He realizes that if he doesn't try at something, he'll be a bum forever:
ROCKY: All I wanna do is go the distance. […] And if I can go that distance, see, and that bell rings and I'm still standin', I'm gonna know for the first time in my life, see, that I weren't just another bum from the neighborhood.
Rocky's an American hero for a few reasons: his iconic training montage, his affable sweetness, and his "started from the bottom, now I'm here" reward. But maybe his heroic status stems most from the fact that he always stays true to himself.
At the end of the movie, Rocky is still a sweet dope with fists of steel, but he's a sweet dope with fists of steel who went the distance with the heavyweight champion. He's always been a survivor, but by surviving fifteen rounds with Apollo, he finally learns to believe in himself.