I think this song is about denying a part of yourself and giving up youth and innocence to become an adult in the world. (What you've seen isn't part of me at all). He was too quick to turn his head meaning he wanted to grow up fast and be an adult, but he didn't know what it meant, this particular lyric is a painful reflection and longing of childhood innocence.
"I had to go just to get around, other way around": in order to function in the world ad an adult, he turns part of himself the other way around, essentially betraying morals of his true character or innocence or whatever just to get around.
I think this song is about denying a part of yourself and giving up youth and innocence to become an adult in the world. (What you've seen isn't part of me at all). He was too quick to turn his head meaning he wanted to grow up fast and be an adult, but he didn't know what it meant, this particular lyric is a painful reflection and longing of childhood innocence. "I had to go just to get around, other way around": in order to function in the world ad an adult, he turns part of himself the other way around, essentially betraying morals of his true character or innocence or whatever just to get around.