The Work of God

And I am sure of this, that he who began a good work in you will bring it to completion at the day of Jesus Christ.    (Philippians 1:6 ESV)

"I am sure..." - Paul is confident. Not in himself, but in the Lord Jesus Christ whom he serves.
"He who began a good work..." You didn't begin this work in your life. God the Father sent God the Son into the world to be the perfect sacrifice for your sin and mine. God the Son perfectly obeyed the will of His Father, not just in His sacrificial life, but also in His perfect, Law-obeying life. God the Father accepted God the Son's death and life as the atonement for our sin as if we perfectly obeyed and also as if we atoned for our sin. God the Son rose from the dead and sent His Holy Spirit to begin a good work in us. This good work is the work of God the Son.
"He who began a good work in you will complete it ... " God's work in you is on it's way to completion everyday. That completion will be at the return of God the Son to establish His eternal kingdom on earth. And because God started it, and God completes it, the work of God in the life of the believer will be a HUGE SUCCESS... Eternal life.  Our salvation is about God, not us... remember that and rejoice in that today. Because of Christ, we CANNOT fail!