Achievements, luck and value

Achievements are clearly something that we care about. We want a life rich in achievements, and we value the achievements of others. To be appointed to the job of one's dreams as a result of one's hard work and raw talent, such that it constitutes an achievement on one's part, is far more satisfying and worthy than getting it through other means where no achievement is involved (e.g. as a result of nepotism). Similarly, the Olympic goal medal winner who gets her award by being the best in a strong field exhibits an achievement and is lauded for it, but her counterpart who attains the same result through, say, mere good luck (e.g. none of her competitors is able to compete due to injury), and who thus does not exhibit an achievement, is not gifted nearly as much praise. But what is an achievement, and what is it about achievements that makes us care about them so much?