Matthew 6:13 - And do not lead us into temptation, but deliver us from the evil one.
There is no temptation or sin in heaven. This prayer does not imply that God wants to tempt us. We know from James 1:13 that it is impossible for God to entice us to sin.
This kind of praying is important because it requires us to face our need for grace. It helps us to align our heart with heaven -- one of absolute dependency on God.
The phrase "deliver us from evil", as it is traditionally rendered, actually means, "deliver us from the evil one." A heart modeled after heaven has great success in spiritual warfare. Jesus was able to say, "satan has nothing in me."
The believer is to be completely free from all satanic influence and attachments. That is the cry voiced in this prayer.