My mother and I have debated over the years about the fundamental nature of humans. She believes people are fundamentally good. I believe people are fundamentally bad. I came upon this belief through a combination of the christian concept of original sin and life experience. I particularly like the video linked above where a Navajo elder describes the traditional Navajo (Diné) belief that people are basically bad and that evil exists.
Mom also grew up in the christian faith but apparently original sin never took with her. She also grew up in the rural Deep South and views human society like Mayberry from the Andy Griffith show. It must have been nice to have lived in that type of friendly society (except for the poverty), but I can't reconcile that view with my life experience. I've known too many bad people and seen too many acts of evil.
|The Sin of Adam and Eve, by Michelangelo - Web Gallery of Art: Image Info about artwork, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11421186|
I believe we all have evil urges and tendencies to fail. What this means is that life is a contest of you against the evil and failure inherent in your being.
You were born to be evil. If you don't want to be evil, then you have to make yourself be good. This requires self-discipline.
Inattentiveness to what you are doing results in failure by default. In order to succeed, you must pursue success mindfully, or at least actively avoid failure. This too requires self-discipline.
You can't always succeed and you can't always avoid sin so living correctly requires constant effort. Life requires self-discipline and there is no end to it. It's a method for living, not a target that you can hit.
Keep grinding at the process. That's self-discipline.