What was the change in Peter? The upper room was the change. He and those who spent time with him in that room waited for the third person of the triune Godhead to invade their lives. The Holy Spirit came to them after they prayed through. What does that mean? They gave up everything. They emptied themselves of self and let God have control of their lives. They vowed to do what God asked them to do…whatever it might be or whatever it might cost. Peter and those with him held nothing back.
You can do the same. It’s not just the words, “I give myself to you,” though. It means you have to really do it. You really pray through and give God everything…everything. It’s not always easy to give everything up, but you must give Him everything if you expect to have the strength of those like Peter, Paul, James, John, and so many others through the centuries.