Christians, if Jesus is God then why did he pray to himself?

Jesus is also fully human. All humans must pray to God. If you allow His Divinity to interfere with the humanity of Jesus, then Jesus could not be truly human. Jesus is BOTH really God and really human. Neither nature can be used to negate the other. One cannot pit one nature against the other in order to prove it is not true. Jesus is truly human with His Divinity fully intact. This is known as the mystery of the hypostatic union.

God is three beings. The trinity has separate roles. Jesus was praying to His Father because that is who we are to pray to.

The biggest confusion probably lies in the idea of more than one mind in ONE being. That throws off a LOT of people.

Look at it this way. You have a mind that is 100% human, correct? Your father has a mind that is 100% human too, right? Your minds, though separate, are both 100% human.

The same happens in the Trinity. The "Father's" mind is totally divine, as is the Son's (though his mind is united with and expressed through a human mind as well). Both the Father and Son have separate minds, but their minds are still divine, and thus are different mental expressions of DIVINITY. Father and Son are ONE divine being, with two different mental expressions divinity (ie, two different minds), who are nonetheless UNITED in the essence of divinity ITSELF. It is the HOLY SPIRIT which UNITES Father and Son, and it is the Holy Spirit which IS the essence of "divinity" itself.

Jesus is united with his Father in divinity, in much the same way as you are united with your father in humanity.

Does that help?