There is the faith of the fallen man who, being shown the grace of God, wants to believe, wants to receive, and there is the faith of the Son of God, Who lives in me, and believes, and I share in Him, and have life.
These are two very different kinds of believing.
There is the trust in God formed in my character, the plasticity of the brain, as I choose trust, and as I trust, my brain is re-writing neural pathways, establishing a greater character to trust. I can forget Christ in me, and rely on this trust, partial, fallible, it's a faith that comes from myself.
There is a trust in God which is the life of Christ in me. As Jesus trusts His Father that trust is expressed through my life, in the same way that as Jesus loves others, that love is expressed in my life, and as Jesus is self-controlled, that self control is expressed in my life.
2 Corinthians 3:18 KJV
17 Now the Lord is that Spirit: and where the Spirit of the Lord is, there is liberty.
18 But we all, with open face beholding as in a glass the glory of the Lord, are changed into the same image from glory to glory, even as by the Spirit of the Lord.
If we trust in Jesus and walk in the Spirit we have complete liberty, we don't have to concern ourselves with ourselves. We need not be self-conscious, because the Spirit is leading our steps. And I'm not saying we are impeccible, rather the Holy Spirit will bring to our awareness such things as we need to know, and otherwise our focus is on others, and on God Himself. That's simply the life of the Spirit, that's what our minds will be filled with.
As we walk in the Spirit (a normal Christian response to trusting in the completeness of our reconciliation in Christ) we see the life of the Spirit, Jesus' life, expressed in ours. We learn by experience, by living it, what Jesus is like, Who He is. And as we live it, neural pathways are written into our "brain plasticity" brains, changing our character, how we think, this is the renewing of the mind.
We do such things as are God's love to others, the very reason we are still on the earth, the "true holiness" of Ephesians 4:24. Living this way cannot help but change us, and it gets easier to live this way, because at least SOME of the corruption of the flesh is being corrected, though it will never be complete as long as we live in these corrupted flesh bodies.
Just the same, we are not our flesh. Sin lives in the flesh, and we do not, we live in Christ. We occupy this world by means of our flesh bodies, but our lives are hid in Christ, where we are seated together.
If we could only SEE the new reality we live in since we've been submerged into Christ!! But our walk is by faith, not sight, and we have His Word, now we must believe it.
If we think we see something in ourselves that disqualifies us from our communion with God, we may stop trusting in Christ for our acceptance, and fall out of that grace.
When that happens the better we've been able to build our character, the more that will help us, as that's helping restore some of the damage to the flesh, and in particular the fleshy brain.
To the extent we've been able to re-write our brains through making better choices, and working them out with better behavior, the easier time it may be for us until we realize, "This isn't that same faith that made life so abundant!!", and seek to return to the walking in the Spirit, where we just don't have to be concerned over such things as a general rule.
Much love!