Discipline

I want to be disciplined, not because it's expected of me, but because things need to be done. When I look at all my responsibilities, I realize everything I do is expected by an outward source. I cook dinner because my children need to eat. I go to work because I'm expected to go to work. I study to learn when I have a teacher to assign me something. When there is no expectation, I do nothing. I know people who will not stop to rest until their house is tidy. They will not sit to watch TV until their self-assigned tasks are complete. I want to be like that! Yet instead, I sit here and type. I didn't drink alcohol until my late 20s not because it was poison for my body, but because abstaining was an outward expectation. Then I observe those claiming not to believe in any higher power also abstain from intoxicating substances. So what is the difference? Why can't I be that disciplined? Once any outward expectations are lifted, I slump like a rag-doll into a pile on the floor. I have no inner discipline. Well...I'll say I have no consistent inner discipline. How do I start?