In developing self discipline the second of the four key factors or components is motivation. If there is no motivation to reach the goal we have set, then disciplining or regulating ourselves to accomplish this goal becomes much harder to do and it is far more likely that we will stop and not reach our goal.
If the motivation is external as in, you have to go to work-not because you want to, you have to study for a test-so your parents do not get mad, you go on a diet because your doctor/friend/spouse says you should, it is not likely that you will be motivated to be disciplined in the efforts.
All of us are motivated in different ways but if we are having trouble with motivation to be disciplined on a specific task or goal, one way putting some pressure on ourselves is to tell our friends and others about the goal that we have and allow them to help us stay the course.
Finally in regard to our children, we may not be sure what motivates them, but our goal is for them to find their motivation from within. With that in mind, external rewards and praise for winning / medals / grades and other external things are less important than helping them to see the results they get with great effort and self discipline. Praising that in our child will help them to continue on the path of self discipline.
Part one: Self Control
Part three: Persistence
Part four: Setting Goals