Simba is so little and so excited to grow up that it's kind of adorable.
SIMBA: Free to run around all day / Free to do it all my way.
Silly little baby Simba assumes that being king means you get to have all the fun in the world all day long while Zazu chases you around, warning you not to slide down the neck of an ostrich.
SIMBA: I was just trying to be brave like you.
After Simba is nearly devoured by hyenas, he learns an important lesson about growing up: you don't need to get yourself into danger in order to prove that you're brave.
SIMBA: No, I'm not the king. Maybe I was gonna be, but that was a long time ago.
As a teenager, Simba doubts himself, assuming he's the one responsible for his father's untimely death.
NALA: Why won't he be the king he is / The king I see inside?
Ever perceptive, Nala wonders why moody teenage Simba won't just grow up already.
RAFIKI: I'm not the one who's confused. You don't even know who you are.
Armchair psychologist Rafiki analyzes the melancholy prince and gets right to the root of his problems: he's got to figure out his life before it passes him by.
GHOST MUFASA: You must take your place in the Circle of Life.
Mufasa's ghost warns his son that it is time to step up to the plate and accept that he's got a life to live, no matter how difficult and fraught that life may be.
RAFIKI: Change is good.
When Rafiki is trying to get Simba to go back to the Pride Lands and become a real adult, he utters the words that every teenager will probably be relieved to hear. Change, though terrifying, is ultimately good—it may be scary and awkward in the moment, but it'll pay off in the long run.
RAFIKI: Oh, yes, the past can hurt. But the way I see it, you can either run from it or learn from it.
If anyone's got a difficult past, it's Simba. Rafiki helps him see that in order to grow up, he's got to learn from it and move on.
SCAR: Mufasa—no! You're dead!
By the time Simba returns to the Pride Lands, he's grown up so much that Scar actually mistakes him for Mufasa. Circle of Life, bro.