To separate faith from confidence would be an attempt to take away heat and light from the sun. I acknowledge, indeed, that, in proportion to the measure of faith, confidence is small in some and greater in others; but faith will never be found unaccompanied by these effects or fruits. A trembling, hesitating, doubting conscience, will always be a sure evidence of unbelief; but a firm, steady faith, will prove to be invincible against the gates of hell. To trust in Christ as Mediator, and to entertain a firm conviction of our heavenly Father’s love, — to venture boldly to promise to ourselves eternal life, and not to tremble at death or hell, — is, to use a common phrase, a holy presumption. -Calvin’s commentary on Ephesians 3:12
A great quote from Calvin, here. Real faith is going to produce confidence and ultimately boldness in my life. As he makes clear, that confidence will be weak at times, especially as my faith is immature and unformed. But he who trusts in God will know that no power on earth, in heaven or in hell can stand against God’s will for our lives, and God’s will for our lives is that we triumph; not in some carnal sense of fame or money or earthly security, but in God’s completion of the work within us which He started.
This goes to the point I was making earlier about overcoming sin, as well. Overcoming sin is not a matter of working up the willpower to change, or changing my environment. The man who does not believe he can change, who fears to hear the exhortations of God’s law, who sees only condemnation in God’s standards of righteousness, is a man who lacks faith. Overcoming sin is a matter of faith, of believing in God’s promise of forgiveness in Christ and empowering by the Holy Spirit. As I believe those promises, I will gain more confidence to tackle what previously seemed insurmountable, the sin in my life. And as that confidence grows, I will even gain boldness to believe and to do what I never before dared believe or do. I will come to believe that I can indeed be perfect, to be sin-free. Not in this life; not in the strength of the flesh, but by God’s power and enabling, I am even now aiming toward that goal which is promised me in eternity, that I would be truly holy and a worthy image bearer of my perfectly holy savior.
That is, as Calvin says, a holy presumption.