All behavioral and "personality" traits are partly heritable and most (all?) of them are due to many genes of small effects. This is a very general and solid result of behavioral genetics, <<the modern idea that "you can do anything if you just try hard enough">> is made with people who have no clue about the realities of life and speak because they can. It has the same intellectual value as "love will find you."

Although personalities tend to be sticky throughout life, that some people can substantially change their personalities is also quite obvious to anyone with (figuratively) open eyes.