"You could try the two-week posture experiment to improve your own willpower, or you could try other
The key is to concentrate on changing a habitual behavior.
One simple way to start is by using a different hand for routine tasks. Many habits are linked to your dominant hand. Right-handed people, in particular, tend to use their right hands for all sorts of things without giving the matter the slightest thought. Making yourself switch to your left hand is thus an exercise in self-control. You can resolve to use your left hand instead of your habitual right hand for brushing your teeth, using a computer mouse, opening doors, or lifting a cup to your lips. If it seems too onerous to do this all day, try it for a set period. Some research studies have assigned people to switch hands between eight A.M. and eight P.M. This lets people revert to their familiar habits in the evening, when they are already physically tired and mentally depleted from the day’s activities".
"Parents can guide them through the kind of willpower-strengthening exercises we’ve discussed earlier, like taking care to sit up straight, to always speak grammatically, to avoid starting sentences with “I,” and to never say “yeah” for “yes.” Anything that forces children to exercise their self-control muscle can be helpful: taking music lessons, memorizing poems, saying prayers, minding their table manners, avoiding the use of profanity, writing thank-you notes".
Excerpts from, Willpower: Rediscovering the Greatest Human Strength - Roy F. Baumeister, John Tierney