You go out into your world, and try and find the things that will be useful to you. Your weapons. Your tools. Your charms. You find a record, or a poem, or a picture of a girl that you pin to the wall and go, "Her. I'll try and be her. I'll try and be her - but here." You observe the way others walk, and talk, and you steal little bits of them - you collage yourself out of whatever you can get your hands on. You are like the robot Johnny 5 in Short Circuit, crying, "More input! More input for Johnny 5! as you rifle through books and watch films and sit in front of the television, trying to guess which of these things that you are watching - Alexis Carrington Colby walking down a marble staircase; Anne of Green Gables holding her shoddy suitcase; Cathy wailing on the moors; Courtney Love wailing in her petticoat; Dorothy Parker gunning people down; Grace Jones singing "Slave to the Rhythm" - you will need when you get out there. What will be useful. What will be, eventually, you?
And you will be quite on your own when you do all this. There is no academy where you can learn to be yourself; there is no line manager slowly urging you toward the correct answer. You are midwife to yourself, and will give birth to yourself, over and over, in dark rooms, alone.
And some versions of you will end in dismal failure - many prototypes won't even get out the front door, as you suddenly realize that no, you can't style-out an all-in-one gold bodysuit and a massive attitude problem in Wolverhampton. Others will achieve temporary success - hitting new land-speed records, and amazing all around you, and then suddenly, unexpectedly exploding, like the Bluebird on Coniston Water.
But one day you'll find a version of you that will get you kissed, or befriended, or inspired, and you will make your notes accordingly, staying up all night to hone and improvise upon a tiny snatch of melody that worked.
Until - slowly, slowly - you make a viable version of you, one you can hum every day. You'll find the tiny, right piece of grit you can pearl around, until nature kicks in, and your shell will just quietly fill with magic, even while you're busy doing other things. What your nature began, nature will take over, and start completing, until you stop having to think about who you'll be entirely - as you're too busy doing, now. And ten years will pass without you even noticing.
And later, over a glass of wine - because you drink wine now, because you are grown - you will marvel over what you did. Marvel that, at the time, you kept so many secrets. Tried to keep the secret of yourself. Tried to metamorphose in the dark. The loud, drunken, fucking, eyeliner-smeared, laughing, cutting, panicking, unbearably present secret of yourself. When really you were about as secret as the moon. And as luminous, under all those clothes.