Dallas Willard on simple prayer, which I found very helpful:
“Prayer, like all of the practices into which Jesus leads by word and example, will be self-validating to all who will simply pray as he says [that is, the Lord's Prayer] and not give up. It is much harder to learn if we succumb to the temptation to engage in “heroic” efforts in prayer. This is important. Heroism, generally, is totally out of place in the spiritual life, until we grow to the point at which it would never be thought of as heroism anyway.
“There are, of course, people who pray heroically, and they are to be respected for what God has called them to… But that is a special calling and is for very few of us. To look to this calling as the ideal for our prayer life is only to assume a burden of uncalled-for guilt, and, quite surely, it is to choose an approach that will lead to abandoning prayer as a realistic…aspect of life in the kingdom. There will be heroic periods as they may be called for, but with no intention to be heroic. Always, we are simply children walking and talking with our Father at hand.
“…Prayer is never just asking, nor is it merely a matter of asking for what I want. God is not a cosmic butler or a fix-it man, and the aim of the universe is not to fulfill my desires and needs. On the other hand, I am to pray for what concerns me, and many people have found prayer impossible because they thought they should only pray for wonderful but remote needs they actually had little or no interest in or even knowledge of.
“Prayer simply dies from efforts to pray about “good things” that honestly do not matter to us. The way to get to meaningful prayer for those good things is to start by praying for what we are truly interested in. The circle of our interests will inevitably grow in the largeness of God’s love.
“What prayer as asking presupposes is simply a personal…relationship between us and God, just as with a request of child to parent or friend to friend. It assumes that our natural concerns will be naturally expressed, and that God will hear our prayers for ourselves as well as for others. Once again, this is clear from the biblical practice of prayer. It is seen at its best in that greatest of all prayer books, Psalms.
Accordingly, I believe the most adequate description of prayer is simply, “Talking to God about what we are doing together.””
~ Dallas Willard, The Divine Conspiracy: Rediscovering Our Hidden Life in God, pp. 241, 242, 243.