Faith is built in the soul when you renew your mind with God's word. If you do not renew your mind, then the fallen nature of man drives your bus. When you were born again, your spirit man/person was reborn, but you didn't get a new brain. Our mind needs to be re-programmed much like a computer. Input - output, what goes in is what comes out!
Faith is given life with your body. Words and actions give birth to the seeds of faith that are being developed inside as you renew your mind and fellowship with God. We live what we believe. Our actions are reflections of who we serve.