Both "potential" and "power" can be traced back to the Latin word "posse," which means "to be able." When you have the potential to become or accomplish something, you are able to do it, but outside forces (such as the persecution faced by Anne Frank) or traits in your own nature (such as laziness) can stop you. "Power" is the ability to act or produce an effect. Still another "posse" descendant is hiding in our question. The word is "possibility," from the adjective "possible," which of course means "being within the limits of ability or realization."