Most of your behavior, good or bad, is determined from the experiences you had from the time you were conceived to the time you became 12 years old.
If you had a hard time in the womb, this will reflect on what type of person you will become. If you had a hard time during birth, this also will affect your personality. If you were abused and not loved up until you became 12 years old, your behavior and personality will be set for the rest of your life.