Prayer is a communion between earth and heaven. It is a request made by man on earth to the Divine who dwells in the unseen. But this man on earth follows the will and promises of heaven on earth: 'Thy will be done on earth as it is in heaven.' On the question of heaven, you have to have Divine presence within you just as the Master said that the kingdom of God is within you, and that's because you have received the Holy Spirit and become the temple of God. This is what makes it possible for you to live on earth as it is in heaven.