Willpower is not that powerful.
Movies will celebrate athletes, military heroes, and leaders who appear to have super human will; but the rest of us are usually languishing in our efforts to beat our social media addiction, start an exercise program, and find some patience with our kids. Our will seems feeble and prone to any excuse in the world to do the opposite of what we want it to do.
The reason that our will seems so lacking to actually help us change is because we haven’t placed it under the will of God. We think all change has to start with us with hope that God will intervene at some point. The reality is that God initiates the desire to change, God provides the vision and intention to change, and God reorients our will so that it is habitually attuned to what is good and right. Our role is to surrender to the work of God on our will. We have to pray to want what God wants. We have to get to that part of the Lord’s Prayer where we say, “Thy kingdom come, thy will be done,” and actually mean it. We have to determine that the only thing that I want and desire is for God’s will to be done, even if that will seems, at the time, out of my preferences and I can’t see any good in sight.

If our human will is given a Godly nature, think about what effect that would have on the rest of ourselves? Your mind that wants to worry and scheme now only wants God to have his way. Your body, which is obsessed with its own wants and prone to veer far from God, now is primed for doing what is right. Our social dimension, which often pressures us in negative directions and conflict, now is full of humility and desires for others to prosper. “Let each of you regard one another as more important than himself; do not look out for your own personal interests, but for the interests of others.”
To get to this point it takes surrender but it also takes practices that are exercises in turning important things over to God. In fasting, we turn our physical desires over to God and find that he sustains us. In Sabbath, we turn our time over to God and find that God controls the world just fine without all of our activity. In service, we turn our selfish interests over to God and find that God has much to teach us about how to find fulfillment.
It must be emphasized that the practices are simply opening us up to letting God do more in our lives and are not a self-generating effort to change. God does the changing, we are surrendering ourselves over to that change, no matter what it takes.
This is how to find true power of will, not from ourselves, but from the God who longs for us to live as Grown Up Christians, Children of Light, and sons and daughters of the most high king.