If Jesus was God himself, then why did he say...?

Jesus was God-incarnate which means he was a human, but with the powers of God. His body could be hurt and weakened just like everyone elses, but he could perform miracles no other human could. You also have to remember what Jesus was going through at that moment. He was in extreme pain, and his faith in God was nearly depleted. He could have easily escaped his captors and gotten away easily, but he didn't and instead took the hard way so he could sacrifice himself for us.