If God is Not Sovereign in Salvation Then Why Pray?

I was listening to a message on the Sovereignty of God in Salvation today by Michael Horton and he made an excellent point. Have you ever been asked, "If God is determines who will be saved, then why pray for someone to be saved? If it has already been determined, why pray. Horton went on to say, "Not only does God determine the end, but he determines the means as well". But then he said, "Really we should be asking them, if God is NOT Sovereign, then why pray for the salvation of anyone? Since God has done all he can and he is just waiting for the poor sinner to choose Him and God is helpless in determining the eternal destiny of a man, then why pray to ask God to save anyone? I thought this was an excellent point that he made which I had never considered before and wanted to share it.

For we know that God is in control of all things, including the salvation of men. We pray to Him, because we know that God can change a mans heart if God is willing and has compassion on the man. Amen?