When Jesus spoke with Nicodemus early in His ministry He explained that the Holy Spirit in His followers’ lives is like the wind. The wind cannot itself be seen, yet its presence can readily and undeniably be observed. If you see a tree branch moving, a kite flying, or hair blowing you can be sure that there is wind present. In the same way, the presence of the Holy Spirit in a person’s life cannot be seen but His impact upon them can. Believers live differently than they used to before trusting in Jesus and increasingly in compliance with God’s will – and that can be seen.
The wind has both direction and strength. The Holy Spirit provides both, as well. He directs a Christian’s desires and decisions so that their will is aligned and compliant with God’s will and ways. They want to do what God wants them to do. The Holy Spirit also provides strength, both the impetus and energy to do what pleases God. Living in ways that God decrees seem onerous and impossible to non-Christians, yet enabled by the Holy Spirit’s direction and strength in actuality it is neither.
The Acts of the Apostles, Part 63 – Outline (PDF)