Self and personality emerge out of experience, that is why you should stay totally open to the possibilities provided by each moment, and to let experience shape the self. The person lives in an environment of permanent change, yet often and moreover too easily, people oppose this fluidity and instead build constructs of how they think things should be. Your preconceptions about how the world is, or should be, and your own role within it, narrow your world and diminish your ability to stay present and open to experience. The experience should be at the beginning of the construction of your personality, rather than trying to fit your experiences into a preconceived notion of our sense of self.
One of the important parts of Carl Roger's person-centred therapy is not living in the past or in the future. He placed emphasis on the person's current perception and how we live in the here-and-now. "To open one's spirit to what is going on now."
When you move towards openness, you find you also makes progress in your ability to trust yourself and your instincts, and start to rely more calmly on your decision-making capabilities. You are able to see more precisely what direction your real self wants to take, and can make choices that are truly in relevance with your needs. No longer at the mercy of what you think you should be doing, nor of what society or parents may have conditioned you to think you want, you can much more easily simlpy exist in the moment and be fully aware of what you actually want.
In living "the good life" you also have a sense of owning your live and taking resposibility for yourself. What you choose to think or do is down to you; there can be no residual resentment when you have truly identified for yourself what you want and need, and taken the steps to achieve it. At the same time it is greater accountability and an increased tendency to truly invest in your life.
Achievements are to be recognized, but they are independent and secondary to acceptance, which is a basic human need, and does not have to be "earned" through deeds of action. Rogers says that the value of an individual is inherently granted merely by miracle of existence. Acceptance must never be thought as something conditional; unconditional positive regard is crucial to how we might all live "the good life".
If you are interested in more psychological concepts, you can find them easily inside "The Psychology Book: Big Ideas Simlply Explained" by DK Publishing.