Is it possible to change your character? And if so, how? 

I don't know, I'm not a psychologist. Clearly there's genetics and clearly there's society. 

They're both very powerful factors. It's like two giant turtles you're standing on. Genetics - wow! Society is wow! And then there's your will.
It's this little turtle thing, some people don't even have it. 

So the whole point is to make this little turtle for the sake of your own happiness in its size and in the volumes it occupies in your soul become bigger than the first two giant turtles. How to do it? There are books and lectures