For in Christ lives all the fullness of God in a human body. So you also are complete through your union with Christ, who is the head over every ruler and authority.

Colossians 2:9-10 (NLT)

The Father sends the Son for our salvation and the Son sends the Holy Spirit for our sanctification.

We are complete in Christ because the Holy Spirit, who resides inside us, secures our completeness. Sanctification is the Spirit's work of revealing our salvation. It is through Him that we experience many fresh and powerful experiences of our completion and fullness in Christ.

To be complete in Christ is to be totally assured that you have a perfect standing, acceptance, and relationship with God. You are the object of the same love that the Father has for the Son. The Holy Spirit within you is God's assurance that His love will remain with you and in you forever. If this truth doesn't make your heart glad and fill your mouth with praise, either you don't understand the gospel, or you just won't believe it.

Any attempts to acquire “more” completeness than what you already possess in Christ undermine your friendship and relationship with God. You are missing out on the amazing sweetness of your salvation in Christ if you are straining and performing in order to win God's love and favour. Such a mindset transforms you from a loving child of God into a spiritual orphan.

The sanctifying work of the Spirit empowers you to obey and walk in the truth of your identity in Christ. In other words, He is helping us to live a life that brings God the most glory. Obedience is an essential mark of someone whose heart has been moved by the Spirit of grace. When we learn to appreciate our completeness and fullness in Christ, the desire for sin diminishes and the desire to obey God increases.

Our complete fullness in Christ is both the testimony and evidence of our salvation and sonship. Then we will not feel and behave like spiritual orphans, but act and walk as true adopted sons and daughters of God.