If Jesus is God, why does he pray to God throughout the new Testament, and encourage us to worship God? And why did Jesus call out "My God my God why have you forsaken me" if he is God?
In discussing what is sometimes referred to as the doctine of the "trinity" I will have to start by admitting what the Bible says on this subject is difficult to grasp. In fact, it is not even "logical" according to human ways of thinking. Let us look at John 1:1. In the beginning was the Word, and the Word was with God, and the Word was God." Further down, in John 1:14, it says that "The Word became flesh and lived for a while among us." We know that John is talking about Jesus. Imagine this. Imagine that I said I am with my wife and I am my wife. That would be confusing, to say the least, and evidence that I am not in my right mind. However, at first glance this seems to be what John says about Jesus. Let me give the classic understanding of this passage, which is also what I believe to be true. Jesus is deity. Jesus is God. Jesus, the Son and God, the Father are one (John 10:30). God is one, yet he is three, as the Holy Spirit is also deity. The Father and the Son are not created. They are of the same essence, yet in a way which will be a mystery until the end of this age, they are two "persons." Passages which flesh out this doctrine include Colossians 1:15-19 and Hebrews 1:1-4. This is deep stuff, yet it is what God says about himself in the New Testament.
In this context, to answer your question, Jesus, even though being God, submitted to the other person of God, his Father (Philippians 2:6, John 12:49-50). Jesus was in nearly constant prayer and communication to the Father, as you can find by studying through any of the gospels. He calls attention to himself, but even more so to the Father. In John 14:6-7, he says "No one comes to the Father except through me. If you really knew me, you would know my Father as well." I will have to say that at first, it is hard to see how it is logical that Jesus is God, yet he prays to God the Father. Yet, this is exactly what is taught in the New Testament. You may have to chew on this one a while to take it in. I suggest you give the Gospel of John a very careful reading in this light.
As to the emotionally charged question of Jesus while on the cross, "My God, my God, why have you forsaken me?" this is one of the most emotionally wrenching passages in all of scripture. It is also potentially confusing for one who understands from the scripture that Jesus is God but does not understand the idea of the "trinity." Is Jesus talking to himself? Is he schizophrenic: disowning himself? The answer is an emphatic no!!! The scene at the cross is the culmination of the entire gospel. We sinned. "The wages of sin are death." (Romans 6:23). "All have sinned and fallen short of the glory of God." (Romans 3:23). God the Father chose to put onto Jesus the Son the penalty for our own sins so that we might be made right with God–be renewed to a relationship with God despite the sins which would otherwise condemn us. If you look at the story of Jesus in the Garden of Gethsemane (Matthew 26:36-46), you see that Jesus, despite being deity, struggled with what his Father asked him to do, yet he said, "Not my will, but yours be done." Is prophesied in Isaiah 53:6, "We all, like sheep, have gone astray, each of us has turned to his own way; and the Lord has laid on him the iniquity of us all." Jesus took on his shoulders of all the sin of the world while crucified for our sins on the cross. At this point the Son, beloved of the Father, was rejected and took on the anger and the justice of God. For the first time, the Father looked away from the Son, and Jesus cried out in the deepest, most unimaginable anguish, "My God, my God, why have you forsaken me?" Is this because Jesus did not understand why? No. It is a cry, not for information but of anguish. This, in essence, is the gospel message.
John Oakes, PhD