When Paul speaks about Christian sanctification, he relates it to the Holy Spirit.
This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh. (Galatians 5:16)
Our walk is by the Spirit; we walk in accordance to His promptings. Just as the Spirit led our Lord, so are we to be led by the Spirit.
If we live in the Spirit, let us also walk in the Spirit. (Galatians 5:25)
We not only walk by the Spirit, but even our whole life can be said to live by the Spirit.
But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith, Meekness, temperance: against such there is no law. (Galatians 5:22-23)
The gamut of Christian experience is the product of the Holy Spirit, the fruit of the Spirit; all the virtues, so beautifully expressed in Christian life, are really the fruit the Spirit produces within a Christian life. You can see that even our sanctification is a product of the Spirit.