The first three petitions have to do with the honour and glory of God. Christians love God, and so their prayers are not an attempt to "use" God. They desire his glory. Only now do our needs come into the picture in this fourth petition.
Dependence
Praying for our daily needs expresses our dependence on God, the opposite of that pride with which men delude themselves that they are in control. If there is one thing we should learn from the present foot and mouth outbreak, it is that God can take away, in his judgement, any of the material blessing that as a nation we have taken for granted for so long. We are to love God with all our strength, and therefore can only sincerely ask God for daily provision if we desire to serve him in our daily lives. How sinful to expect God to provide for us so that we can live lives in rebellion against him!
Thanksgiving
If we depend on God for our food and necessities, we ought to thank God for what he does provide. Christ himself gave thanks before meals, as did the apostles, Mark 8:6, 14:23 and Acts 27:35. To not do so is to behave like an atheist, whatever we may profess.
Confidence
The words "this day" tell us that we should be content if we have today‘s provision and trust God for tomorrow‘s. That does not mean we do not engage in lawful labour, but we leave the outcome to the providence of God.
Contentement
This petition indicates the need to be content with what God provides. Contentement is not a mark of an ungodly age like ours.
"Let your conversation be without covetousness; and be content with such things as ye have: for he hath said I will never leave thee, nor forsake thee", Hebrews 13:5.
Covetousness is that discontented craving for that which is not ours. Ungodly men and women are often tormented with such sinful desires - to have what others have, to keep up with others etc. Contentment is in knowing Christ and knowing that his promise applies to us, "I will never leave thee, nor forsake thee".
Non-Christians cannot be content, because their sins are not forgiven, they are not at peace with God, and they face his judgement in the world to come. But for those who have trusted Christ, who bore the guilt of sin on the cross, contentment is attainable.
The more they appreciate Christ’s greatness and the truth of his promises, the more content they will be. "But godliness with contentment is great gain. For we brought nothing into this world, and it is certain we can carry nothing out", 1 Timothy 6:6-7.