"The example of Asa, 2 Chron. xvi. 12, teaches us in this case not to lay too much trust upon the physician, but with Hezekiah first look up to God, and then use the means, 2 Kings xix. 14, 15." Richard Sibbes (Works, 1: 240)
Going through Volume 1 again m'self this year. I think Sibbes -and this especially comes out in The Bruised Reed and The Soul's Conflict- is the pastoral example par execellence with not comforting the hypocrite/formalist, while also refusing to allow the tender conscience to despair.
As to the subject matter, I love the pithy way Gurnall said it, "Be careful not to trust in the armour of God, but in the God of the armour."
I read through Gurnall last year. I cannot recommend him enough. I would recommend him to nonPBers, but realistically his 17th century style and illustrations are too much for many modern readers. Has anyone (on PB) read the daily devotional book taken from Christian in Complete Armour?