I liked September 11's page from this devotional book a friend recently passed on to me:
PRAYER CHANGES US
Your Father knows what you need before you ask him. Matthew 6:8
You might wonder, "Why does God insist that we pray to him and tell him our problems? Why doesn't he take care of us without our having to ask? He already knows what we need better than we do." God continually showers his gifts on the good harvests, money, healthy bodies, and so on. But no one asks God for these gifts or thanks him for them. If God already knows that we can't live without light or food for any length of time, then why does he want us to ask for these necessities?
Obviously, he doesn't command us to pray in order to inform him about our needs. God gives us his gifts freely and abundantly He wants us to recognize that he is willing and able to give us even more. When we pray, we're not telling God anything he doesn't already know. Rather, we are the ones gaining knowledge and insight. Asking God to supply our needs keeps us from becoming like the unbelieving skeptics, who don't acknowledge God and don't thank him for his many gifts.
All of this teaches us to acknowledge God's generosity even more. Because we continue to search for him and keep on knocking at his door, he showers us with more and more blessings. Everything we have is a gift from God. When we pray, we should express our gratitude by saying, "Lord, I know that I can't create a single slice of my daily bread. You are the only one who can supply all of my needs. I have no way to protect myself from disasters. You know what I need ahead of time, so I'm convinced that you will take care of me."