"For it is God who works in you both to will and to do for His good pleasure" (Philippians 2:13). God's good pleasure is in you, when the Holy Spirit works in your life. The Holy Spirit works in you through the abiding gifts of faith, hope and love (1 Corinthians 13:13).
God works in all who truly believe on the Lord Jesus Christ (1 Corinthians 6:19). God is working in you to do his will. God changes your heart (Romans 2:28-29). That's called regeneration or new birth. He gives you a renewed will with a desire to do his will.
God works in your mind, will, and emotions. He is doing more in you than you can understand. He is always doing more than you ask or think (Ephesians 3:20). God is working in your heart to bring glory to His name. God gives you the ability to do all that pleases him. That includes your ministry gift and power to witness for Christ (Acts 1:8; 1 Peter 4:10-11).
As a believer, God works in you through the Holy Spirit. He will never leave you nor forsake you (John 14:16-17). Believers are sealed with the Holy Spirit until the day of redemption, at the coming of Christ (Ephesians 1:13, 4:30). God who began the good work in you will perform it until the day of Christ (Philippians 1:6; 2:13).