This is a great quote from a famous coach - one that my son-in-law admires very much. It's true to the point that it takes an amount of confidence in yourself to be able to make substantial changes in your life. The older you get the harder it is. I know some folks who have done it. I've watched them turn around and go in a completely different direction after years of established habits and patterns.
I would like to add, however, that those who have a relationship with God through Jesus Christ, have the advantage of drawing on His very power, even when they are desperately weak, to continue to integrate those changes into their body (new ways of acting), their mind (it all starts with new thoughts) and their spirit (where the lasting motivation lives).
For You are my hope, Lord GOD , my confidence from my youth.