Luther begins his exposition of the Lord's Prayer by saying, "With these words God tenderly invites us to believe that He is our true Father..." and so He is. The prayer that Jesus taught is one that is applicable in every situation we experience in life. Prayer is not simply a matter of spewing information to God, it is a matter speaking simply and honestly, reading His Word, and living out our daily vocations. This is what St. Paul means by saying that we are to "pray without ceasing." Our prayers end with "amen" as Luther says, because:
God has briefly placed before us all the distress that may ever come upon us, so that we might have no excuse whatever for not praying. But all depends upon this, that we learn also to say "Amen." This means that we do not doubt that our prayer is surely heard and that what we pray shall be done [2 Corinthians 1:20]. This is nothing else than the word of undoubting faith, which does not pray on a dare but knows that God does not lie to him [Titus 1:2]. For He has promised to grant it (Martin Luther, The Large Catechism, para. 120).
Below you will find the series of sermons and services about the Lord's Prayer and hear of the wonderful ways God desires us to call on Him.