The most important aspect is the environment though. Since our childhood, we go through different experiences in life that help us in shaping our personality. When the hero who was singing sad songs was prompted by the crowd to sing something happy he then sings some thing like this if translated. I am in deep sorrow how can I bring happiness in my songs. I am going to give to this world what I will get from this life.
Different aspects including heredity influence our personality.
The most important aspect is the environment though. Since our childhood, we go through different experiences in life that help us in shaping our personality. Unfortunately, people who we find difficult and full of anger are the people who have had some bad influences in their life. Most of the time, we try to avoid such people since we do not click with them. However, if they are the people we can't avoid we need to deal with them.