When you pray, consider what you want and need and never mind how vulgar or childish it might appear. If you want very much to pass that exam or get to know that girl or boy better, that is what you should pray for. You could let world peace rest for a while. You may not be ready yet to want that passionately. When you pray you must come before God as honestly as you can. There is no point in pretending to him. One of the great human values of prayer is that you face the facts about yourself and admit to what you want; and you know you can talk about this to God because he is totally loving and accepting. In true prayer you must meet God and meet yourself where you really are, for it is just by this that God will move you on from where you really are. For prayer is a bit of a risk. If you pray and acknowledge your most infantile desires, there is every danger you may grow up a bit, that God will grow you up. When (as honestly as you can) you speak to God of your desires, very gently and tactfully he will often reveal to you that in fact you have deeper and more mature desires. But there is only one way to find this out: to start from where you are. It is no good pretending to yourself that you are full of high-minded aspirations. You have to wait until you are. If a child is treated as though she were already an adult, she will never become an adult. Prayer is the way in which our Father in heaven leads each of us by different paths to be saints, that is to say, with him.
Herbert McCabe on prayer in God, Christ and Us.