Agreed. Some people who are highly courageous suffer deeply from akrasia. Other people do not even understand what is meant by the concept of Akrasia when it is explained to them. I do not think that means they have a large amount of willpower; akrasia is simply not an issue for them.

I remember reading about how performing tasks that require a great deal of mental concentration seems to drain an internal reserve of mental energy. As a result, your performance on other tasks that require mental focus also lapses, until you've had time to rest and restore your energy. I would refer to this mental energy reserve as willpower. I think this fits very well with people's experience in fighting akrasia: attempts to use willpower in order to (for example) go on a diet works for a little bit, until all your willpower is expended and you revert to your usual habits.