The opening line of this letter reminds of the words said by the blind Carthusian monk in the film Into Great Silence:
And because He is an infinitely good being, He eternally seeks our well-being. Therefore, there is no cause for worry in any of the things which happen to us. I often thank God that he let me be blinded. I am sure he let this happen for the good of my soul...God is infinitely good, and that all of his actions are in our best interest. Because of this a Christian should always be happy, never unhappy. Because everything that happens is God's will, and it only happens for the well-being of our soul.
Here is the opening paragraph of Brother Lawrence's letter of February 6, 1691
God indeed knows what we need, and everything he does is for our good. If we knew how much he loves us, we would readily accept the bitter with the sweet, and even the most painful and difficult things would be pleasant and agreeable. The most painful sufferings do not ordinarily seem unbearable unless we look at them from the wrong perspective. Furthermore, when we are convinced that it is the hand of God at work in us--that he is a Father full of love who allows us to endure humiliation, pain, and suffering--all the bitterness is taken away, and only the sweetness remains.
I like how he writes about looking at painful sufferings from the wrong perspective. That's what we do all the time.