The fastest way to change yourself is to hang out with people who are already the way you want to be.
Hang around people who are better than you all the time. You do pick up the behavior of people who are around you. It will make you a better person. Marry upward. That is the person who is going to have the biggest effect on you. A relationship like that over the decades will do nothing but good.
If I can stretch this a bit, they don’t even have to be alive! See Austin Kleon:
The great thing about dead or remote masters is that they can’t refuse you as an apprentice. You can learn whatever you want from them. They left their lesson plans in their work.