This is from Amy Carmichael's Edges of His Ways, a devotional taken from her letters to her sisters and co-workers in her work in the Dohnavur Fellowship in India.
This is the devotional I have turned to most often over the years, and it has been a very great blessing to me. I HIGHLY recommend anything written by Amy Carmichael.
Additionally, today's writing fits in so well with what I've learned in A Praying Life by Paul Miller, another book I recommend heartily.
When we pray for something that we want very much, it is good to remember that our Father delights to give us much joy and so there is no need to press Him as if He were unwilling. To do that always seems to me to be unkind. It is as if we had not a very loving Father.
Yet He has told us to ask for what our hearts desire and so it is right to ask, and to ask earnestly, only with this "if" in the depths of our hears, "If it be Thy blessed will, if it be for Thy glory."