What is the relationship between the Holy Spirit’s work and our effort in sanctification?

I think the best place to go for a one-sentence answer to that is Philippians 2:12-13, where Paul urges the Christians to work out their salvation—which is not working up their salvation, but working out the salvation that God has already worked in.

He says, “Work out your salvation in fear and trembling, because it is God who is at work in you, both to will and to do of His good pleasure.”

So we fulfill all the responsibilities that God has given to us in His word as we trust in Jesus Christ and seek the help of the Holy Spirit to fulfill that. So there’s an integrated relationship.

But we are never in a position where we can say, “Oh, that was the Holy Spirit,” and “Oh, that was me,” because what we do is always the fruit of the Spirit working in us.