Sometimes a writer's job is to say what people are thinking, but say it better than they are thinking it. Watch me do that now.
Have you ever wondered who you are? You're not your body, because living cells come and go and are generally outside of your control. You're not your location, because that can change. You aren't your DNA because that simply defines the boundaries of your playing field. You aren't your upbringing because siblings routinely go in different directions no matter how similar their start. My best answer to my own question is this:
You are what you learn.
If all you know is how to be a gang member, that's what you'll be, at least until you learn something else. If you become a marine, you'll learn to control fear. If you go to law school, you'll see the world as a competition. If you study engineering, you'll start to see the world as a complicated machine that needs tweaking.
I'm fascinated by the way a person changes at a fundamental level as he or she merges with a particular field of knowledge. People who study economics come out the other side thinking a different way from people who study nursing. And learning becomes a fairly permanent part of a person even as the cells in the body come and go and the circumstances of life change.
You can easily nitpick my definition of self by arguing that you are actually many things, including your DNA, your body, your mind, you environment and more. By that view, you're more of a soup than a single ingredient. I'll grant you the validity of that view. But I'll argue that the most powerful point of view is that you are what you learn.
It's easy to feel trapped in your own life. Circumstances can sometimes feel as if they form a jail around you. But there's almost nothing you can't learn your way out of. If you don't like who you are, you have the option of learning until you become someone else. Life is like a jail with an unlocked, heavy door. You're free the minute you realize the door will open if you simply lean into it.
Suppose you don't like your social life. You can learn how to be the sort of person that attracts better friends. Don't like your body? You can learn how to eat right and exercise until you have a new one. You can even learn how to dress better and speak in more interesting ways.
I credit my late mother for my view of learning. She raised me to believe I could become whatever I bothered to learn. No single idea has served me better.