You are just a bunch of ideas
Personality is a system of ideas all of which must seem to be consistent with one another
- Prescott Lecky
Your personality is a bunch of ideas mixed together. These ideas work consistently with each other and they support each other. You believe these ideas are true. And so that is who you are and who you become - the sum total of these consistent ideas is YOU.
That is why - if you want to change something about yourself, you have to start by changing those ideas about yourself that you believe are true. You have to change those ideas with new ones and start believing that you are something else, that you are someone else.
That is exactly why changing yourself is so hard - just because you have to change your beliefs about yourself. You literally have to believe in something that at first you don't believe. You have to start seeing yourself differently. This is why it is usually so uncomfortable. And that is why noone else can do it for you. Only you believe who you are and who you want to be. Noone else can force you into changing unless you believe you can do it.