Here's an excerpt from Martin Luther's commentary on Galatians:
[Saint Jerome visited by angels by Bartolomeo Cavarozzi]
"Jerome writes of himself: "My face was pale with fasting, and my mind was inflamed with fleshly desires in my cold body, and although my flesh was half dead already, yet the flames of carnal lusts boiled within me." Hereof I myself also had experience when I was a monk. The heat thereof of carnal lust is not quenched by fasting only, but we must be aided also by the Spirit, that is, by meditation of God's Word, faith, and prayer. Indeed, fasting represses the gross assaults of fleshly lust; but the desires of the flesh are overcome not by abstinence from meat and drink, but only by earnest meditation on the Word of God and invocation of Christ."
I think Luther understood faith in a great way. I hear so often in the Church today, either a moral works ethic teaching, where faith is left out, or at the most perhaps tacked on at the end of an exhortation to live moral life; or a cheap kind of faith in my own faith doctrine; I believe in me, and God believes in me teaching. And of course they throw a 'sinners prayer' in the mix, or an 'altar call', where we ask Jesus into our hearts. These teachings, and exhortations, are far from "The Just shall live by faith."
Luther knew that the true faith of a Christian, is crying out to Christ, and the Father, for the Holy Spirit to help. And also, trusting in His Church, and the brothers and sisters we have to help us, by themselves trusting in Christ alone.
But in the end, it's trusting in Christ alone, and not man, nor anything else for that matter, to help us live a godly life for our Savior and Friend, the Lord Jesus Christ, and also our Father in heaven.