A challenging book in the tradition of Christian devotional manuals is The Imitation of the Christ by Thomas A’Kempis. While some of the advice he gives is geared especially or even exclusively toward monks, a great deal of what is said is quite useful advice for appropriating a godly mindset. Here is an excerpt from the first chapter:
What good does it do to speak learnedly about the Trinity if, lacking humility, you displease the Trinity? Indeed it is not learning that makes a man holy and just, but a virtuous life makes him pleasing to God. I would rather feel contrition than know how to define it. For what would it profit us to know the whole Bible by heart and the principles of all the philosophers if we live without grace and the love of God? Vanity of vanities and all is vanity, except to love God and serve Him alone.
Thomas à Kempis, The Imitation of Christ (Oak Harbor, WA: Logos Research Systems, 1996), 1–2.