When we say things like "people don't change" it drives scientist crazy because change is literally the only constant in all of science. Energy. Matter. It's always changing, morphing, merging, growing, dying. It's the way people try not to change that's unnatural. The way we cling to what things were instead of letting things be what they are. The way we cling to old memories instead of forming new ones. The way we insist on believing despite every scientific indication that anything in this lifetime is permanent. Change is constant. How we experience change that's up to us. It can feel like death or it can feel like a second chance at life. If we open our fingers, loosen our grips, go with it, it can feel like pure adrenaline. Like at any moment we can have another chance at life. Like at any moment, we can be born all over again.
Every cell in the human body regenerates on average every seven years. Like snakes, in our own way we shed our skin. Biologically we are brand new people. We may look the same, we probably do, the change isn't visible at least in most of us, but we are all changed completely forever.