Our human nature is indisciplined. No matter how hard we try to live a disciplined life, our nature will always oppose it. Think for a moment.
For example, every time you decide to eat healthy and exercise, this indolent 'flesh' complains. Your body refuses to react when you want to wake up early. Does your body respond well when you have to wake up early for church on Sundays or to go to school in the morning? I guess no. That's why the apostle Paul said, 'But I discipline my body and bring it into subjection.' 1 Co 9.27
We have to train our bodies, discipline them. Discipline is one of the traits of a Godly youth. He is organized, clean, neat. In school, at home, at work, in church, everywhere, specially his spiritual life. In spite of still living in this human body, he makes sure it doesn't have the last word.
So, who is having the last word, you or your flesh?