God works in believers through covenant. What God says, God will do. God's covenant with you is a binding contract. What God promises, God will fulfill. Your faith stands upon the covenant promises of God through Jesus Christ. It is based upon God's covenant word. So then faith comes by hearing, and hearing by the word of God (Romans 10:17).
Now may the God of peace who brought up our Lord Jesus from the dead, that great Shepherd of the sheep, through the blood of the everlasting covenant make you complete in every good work to do His will, working in you, what is well pleasing in His sight, through Jesus Christ, to whom be glory, forever and ever. Amen (Hebrews 13:20-21).
God works in you as a believer through the Lord Jesus Christ. You believe the gospel, that Christ died for your sins, and Christ is risen from the dead. You have entered the everlasting covenant with God by faith in the gospel of our Lord Jesus Christ. Jesus is the Shepherd of all God's covenant people.
God's everlasting covenant cannot be changed, because God has sworn with an oath of promise. The everlasting covenant through Jesus Christ is forever and ever. Amen. Your faith is based upon what God has promised to do in you through Jesus Christ our Lord.
God's covenant promise is to work in believers in such a way to please Himself. Your life pleases God not because you are trying real hard. To the contrary, God is working in you what pleases Him (Philippians 2:13). God's everlasting covenant works in you through Christ.