Will power is not just the equivalent of a muscle, that you need to strengthen gradually. Doing that alone, by choosing to do difficult things or by giving up things that you enjoy but are bad for you. Often for most people doing just that proves to be unsuccessful.
It is the system of values behind the actions that will keep you grounded and on the right path, whenever things will get hard. The precursor for willpower is sacrifice, which is the refusal of the current corrupt reality at any cost in some extreme cases even ones life.
The reason why people fell motivated to say no to corruption at any cost is because, living as a slave it is not particularly a pleasant or even worth living life. Under certain circumstances it is better to die free than live as a slave, which is what motivated so many people to make this choice through out the course of history.
If your choice is a diminished apathetic life, then what does it matter if something bad is going to happen to you or if you are going to experience discomfort in the process of freeing yourself up. The alternative is much worse, because it means living the rest of your life as a slave.
Often what is confusing people is the idea of convenience,
Sacrifice is by nature a selfish and individualistic act, you can't be sacrificed and you can't sacrificed others. You can sacrifice some of your possessions, but at least under natural law there is no slavery, because it is impossible to eliminate free will, so no other living being is truly your possession or a subject for you to sacrifice.
If it is ever demanded of you to sacrifice yourself for a certain cause or the group it is no longer sacrifice, it is abuse. Which is how abusive people will often try to manipulate, to make you think that you are doing something right or noble. When in fact you are just pushing the agenda of evil.
The archetype of the messiah, it is not about someone else sacrificing himself for you and your sins, it is more like an example to follow, it is an blue print to how you can set yourself free.
Without sacrifice there is no willpower, without willpower there is no free-will, without free-will you live in a world of slavery, where the dominant emotion that most people will feel is apathy and the evil dominates.