I'm Jack's What?

Lines running throughout me like text on a page. I am not easily read as the words upon this page. I am unique. I tell a story about you. I know all of your stories, because I was there with you. I am a reminder of your experience, your profession, and your lifestyle. Those that can read me will know your entire life. What am I? I am nothing complex. In fact, I am very simple. I am Jack's two open hands. We use our hands every day, but we don't stop to consider how much we rely on them. They speak our life stories. A musician has calluses on the tips of his fingers. A swordsman has calluses from where he grips the hilt of his blade. I look at my hands and see both of these. A writer has a callus in the crook of his thumb. I am developing one of these. It makes me proud. Our hand are like ring on a tree, if you read them correctly you will learn much. So next you type, write, eat, play guitar, or bang on your drums, remember to appreciate what you have. What would your hands say about you?