The dispositions, aptitudes and attitudes that you were born with serve the learning of your soul. As your soul learns the lessons that it must learn to balance its energy, those characteristics become unnecessary, and are replaced by others. This is how you grow. As you come to realise, for example, that anger leads nowhere, your anger begins to disappear and you move into a more integrated and mature orientation toward your experiences. What once angered you now brings forth different responses.
Until you become aware of the effects of your anger, you continue to be an angry person. If you do not reach this awareness by the time you return home, your soul will continue this lesson through the experiences of another lifetime. It will incarnate another personality with aspects that are similar to your own. What is not learned in each lifetime is carried over into other lifetimes, along with new lessons that arise for the soul to learn, new karmic obligations that result from the responses of its personality to the situations that it encounters. The lessons that the soul has learned also are brought forward into other lifetimes, and this is how the soul evolves. Personalities mature in time, and the soul evolves in eternity." - Gary Zukav (The Seat of the Soul)