2 Timothy 11-12

This is a faithful and trustworthy saying: If we died with Him, we also live with Him; If we endure, we will also reign with Him; If we deny Him, He will also deny, us; If we are faithless, He remains faithful (true to His word and His righteous character) for He cannot deny Himself. 

Faith is believing what Jesus said about what He would do for us and through us and acting upon it. Faith is accepting the Bible as the Word of God and believing that it is true. It takes time and practice and the decision to not be dissuaded from the truth of the word of God.