Praying In The Rain

The Orthodox Divine Liturgy presents an introductory phrase in the form of prayer—as is typical in Orthodox Christianity, there is the prayer before the prayer. It goes like this: "And grant, O Lord, that with boldness and without condemnation we may dare to call upon you the Heavenly God as Father and to say." Why is it a daring thing to say the Lord’s Prayer? Why is it daring to call God "Our Father in heaven"?