Sri Sri Ravi Shankar:
If you think I have no will power, you will never have it. You have locked your own hands, put a label on your forehead that you are weak.
Invoke the valour in you, take a pledge. You have all the force available for you when you need it. You have all the strength and energy.
If someone were to tell you that if you do pranayama for thirty days you would get one million dollars. You will not miss a single day. You may forego sleep, food but not the pranayama. Greed can bring in that power within. Similarly fear- if someone says you would fall sick if you don't do pranayama, you would not miss it.
Love, fear, greed- any one is good to increase will power.
To know intellectually what is good and should be done, you may take it easily and remain in your comfort zone.
Then will power goes down. So enhance your valour or love something with all your heart. Dedication to the cause, fear or greed- these can increase your will power.
Egoistic people are much better than other people because egoistic people have a sense of valour. It is easy to make them commit, get out of lethargy.
People with no ego have lot of love, surrender, its easy for them. Someone who has neither ego, nor valour, nor love, nor devotion, nor greed has no will power. Either become greedy or fearful. But these are very low category. Other one is enhance the love, surrender, true knowledge and enhance your valour.