 
Now all glory to God, who is able, through his mighty power at work within us, to accomplish infinitely more than we might ask or think.
Eph. 3:20 NLT
The problem with my walk with the Lord is not a lack of the person Christ, a lack of the power of the Holy Spirit, or a lack of personal promises from God, but the lack of my desire, will, and determination to walk apart from sin. Just how badly do I want to be holy? That is the question. Often what we lack in our battle with the flesh is a passionate hunger for a holy life.
Why is it that we, in the very kingdom of grace, surrounded by angels, . . . nevertheless, can do so little, and, instead of mounting with wings like eagles, grovel in the dust, and do but sin, and confess sin alternately? Is it that the power of God is not within us? Is it literally that we are not able to perform God’s commandments? God forbid.
We are able. We have that given us which makes us able. We do have a power within us to do what we are commanded to do. What is it we lack? The power? No; the will. What we lack is the simple, earnest, sincere inclination and aim to use what God has given us, and what we have in us.
John Henry Newman, “The Power of the Will,” Parochial and Plain Sermons (San Francisco: Ignatius, 1997), 1175 [paragraphing mine].