I believe this song is just an anthem of youthfulness. It's remincising about being young. "Back then our bones wouldn't break, we didn't give a fuck" and "fighting to stay awake" are things everyone in their youth can relate to. People have the idea that when they are young they are invincible and nothing can hurt them. This is just the writer's way of symbolizing his youth and putting it in song.
I believe this song is just an anthem of youthfulness. It's remincising about being young. "Back then our bones wouldn't break, we didn't give a fuck" and "fighting to stay awake" are things everyone in their youth can relate to. People have the idea that when they are young they are invincible and nothing can hurt them. This is just the writer's way of symbolizing his youth and putting it in song.