The fullness of the Holy Spirit, possession by the Spirit, means to belong wholly to Christ. Nothing is withheld. We must consecrate, dedicate, our whole lives to God.
Dedication is another word for sanctification.
To cleanse is to separate from sin. To sanctify is to dedicate one's life to God. This belonging involves transference of ownership. To live as if we belong in part to ourselves or to the world means we are not fully possessed by the Spirit. We are to consider ourselves purchased by the blood of Christ.