In short, for God's glory yield to his will completely, and never suppose that you could be serving him better in any other way; the best way to serve him is to fall in with his will for us.
He wants you to serve him without joy, without feeling, with repugnance and revulsion of spirit.
Such service gives you no satisfaction, but it pleases him; it is not according to your liking, but according to his.
Imagine that you are never going to be delivered of your anguish: what would you do?
You would say to God: I am yours; if my miseries are agreeable to you, give me more and let them last longer.
I have confidence in our Lord that this is what you would say; then you would stop thinking about the matter, at least you would stop struggling.
Well, do this now, and make friends with your trial, as though the two of you were always to live together.
You will see that when you have stopped taking thought for your deliverance, God will think of it, and when you stop worrying, God will come swiftly to your help.