As you know, the character reflects the personality characteristics that are present in humans. Existential psychologists, in particular, Erich Fromm, shared the characters on the neurotic (harming society) and productive (developing the person and the surrounding society). But can he change? You can change people?
the answer is YES. Rather, it is the answer of psychologists who studied in detail the formation of character. The point is that character, unlike temperament, is formed during life and depends on life situation in which the person is. Temperament is also is a way of responding that reflects the type of our nervous system. The nervous system is unchanged. But the nature of the change, if you change the situation around him!
Take a simple example.
One the boy is hot-headed (that is, quickly excitable, quickly changing the interest) is growing in a defective family of low socio-economic status in the industrial area of Moscow. He didn't have in the life of traveling abroad, did not have higher education and friends from good families. For 25 years he had achieved little: works part time, at the same time, always changing the scope of activities (it is difficult to determine). He was not discouraged, he is always on the positive! Always fiercely takes on new activities. But he always gives up, yells at family, wasting money.
Second the boy is choleric (too emotional, is rapidly changing interest) growing in a complete family, studying in a prestigious school and plays football. He was in Europe, studied from best Moscow experts on business and entrepreneurship. For 25 years he is also "working part time": it is the entrepreneur! Due to his impulsiveness and excitability, he has ensured that his own organization, because at the time, he also vehemently changed the business niches, to find one that really shoots! He had a family, he plans children.
They are very similar, they have the same way of responding to situations. They have similar characters, but different circumstances! Therefore, the nature manifests itself in different ways.
the Output is want to change your character? It is possible. Change the situation around you. Something hurting you? By all means try to fix it or avoid it, if the fix is impossible. Change the circle of communication and contact with those who develop your personality. Change your goal. Think about what you would like to achieve and how. Change yourself for the better and thus change its character!