Do you believe that some people come into your lives for a reason?

why is it most hard core Christians think that God brought somebody into your life so YOU can teach them? did you ever think that maybe they were brought in to teach you something? in my experience God uses the one you would least expect to teach you something. I have tought many and many have tought me. I have seen many on here tell me" how are we to teach you anything when you wont listen?" well who says you are suposed to, maybe I am here to teach you, maybe not who knows? maybe we are to teach other. why do you think you are always right and we are always wrong?