Just before Acts begins, we see the disciples scattered, disillusioned, fearing for their lives, and suffering from self-doubt and personal shame. This is the story of Acts. They are the eyewitnesses to all that has happened to Jesus before and after crucifixion. They faced imprisonment, beatings, rejection, and martyrdom. Apart from their master, they were a pathetic group indeed (Lk 24:11; Jn 20:19). Nonetheless, these men still carried out Jesus' Great Commission. How? Well, the "power" to overcome all of their feelings comes from receiving the Holy Spirit which includes courage, boldness, confidence, insight, ability, and authority. The disciples would need these gifts to fulfill their mission.
If you believe in Christ you can experience the power of the Holy Spirit. Acts is an important book for us today because it confirms that the power which transformed the disciples' lives is the same power that can transform our lives today! That power is, of course, God himself—coming to us through the Holy Spirit.
What area in your life do you need the Holy Spirit to transform?