Each of us is born, we live lives of various lengths, and then we die. We have a separate nature which is our own and which sets us apart from every other person who lives or has ever lived. We share similar characteristics, but each of us is unique. You are you.
What makes us unique is the fact that we perpetually make choices between alternatives. Our choices seem to be far more than mechanical selections based on some complex biological decision making scheme. Rather, your choice seems to be based not only on what you believe will happen if you make a certain choice, but also on what you “want” to happen. You engage in what we will call “rational thought”, whereby you think about many things, including the concepts of right and wrong. You eventually reach a point where that certain quality of being which is unique to you takes over, and you make your choices.
Even though human beings have instinctive feelings for self-preservation, self-satisfaction, etc., you can choose to do the opposite, to go against what your instincts, personality, and emotions tell you to do. You can think about what you are going to do, and can choose to do what you believe is right and good even if it places you in grave danger. Similarly, you can choose to do what you believe is wrong and evil even if you would instinctively do otherwise. Your decision is your decision, a product of your singular existence and being. Able to engage in rational thought, and to choose freely among various courses of action based on those thoughts, you are in a very real sense what you choose to be.