SimchaMinute by Rabbi Avigdor Miller
Middos are considered a permanent, unending form of bechira, of free will. Just as we have free will to choose to do certain things, our character traits are [also] our free will; that’s what you want to do, whether you express it or not.
And therefore it’s of the utmost importance for a person to work on his middos, to change his inner traits of character. — Working on the Middos (#658)