Life is a process of setting and reaching goals. Formulating and achieving worthwhile goals add meaning to life. Even if one's life is very challenging, having worthwhile goals raises the quality of life. The happiest people are those who strive for worthwhile goals, not those whose life is just fun and games.
People with a positive self-image believe in their ability to attain meaningful goals. Someone who has already accomplished worthwhile goals will have an even more positive self-image.
Part of successful goal making and reaching is an awareness of your life mission. People who are clear about their life mission are clearer about their goals. Developing a life mission that inspires and motivates you is one of the most important things that you can do in your life.
(From Rabbi Zelig Pliskin's book: "Building Your Self- image and the Self-image of Others" (Artscroll) Chapter 17)