realising that the Earth does not, in fact, follow a stable orbit. The world does crash sometimes; sometimes it spins too far out of control for you to hold a grip onto things; sometimes it stops completely. And when the world goes off-track ever so often, it takes a while to get it going at the right pace again, lead it back onto the right path. It takes time and effort and you have to find your feet, close your eyes, catch your breath.
Growing up is realising that the heart is not, in fact, the strongest muscle in your body. In fact, it's the weakest. It can tear itself apart at a word, a flashback, at the sight of a face you once knew; it wrings itself dry when you pass by a place that brings back memories, or when you unintentionally revisit old texts and pictures, or when his name appears on your screen. The beating of the heart is subconscious? Nonsense. Each beat is pain pounding at the walls of your lungs, threatening to puncture. It is your brain that is strong, the brain that forces the heart to keep on beating, even if each contraction is a struggle.
Growing up is realising that what people teach you is not what the world teaches you. What you learn from books is not what you know.