My all time favorite devotional is John MacArthur's "Drawing Near" primarily because each day's lesson is filled with practical, biblical wisdom. After a Christian is saved through repentance of sins and submission of Jesus Christ as Lord of their life, the ongoing work of sanctification begins.
One of the daily challenges is keeping a pure mind; thinking about that which is true, honorable, lovely of good repute, excellent and praiseworthy as the Apostle Paul teaches in Philippians. John MacArthur puts it this way, "Jesus said the Kingdom citizen is blessed because he or she has pure thoughts and pure motives that together produce holy living. Someone might claim to be religious and have pure motives, but if his behavior isn't righteous, his heart isn't fixed on God."
To achieve purity, the Lord must be the primary focus and motivation for all we do to His glory, honor and praise. The clean mind and purity of thought that leads to godly behavior comes from reading and studying the Bible, meditating on the scripture, making its application to life situations, prayer and praise in all things ... regardless of the circumstances. These disciplines of obedience to the Lord are not hardships, but gifts from a loving father. I believe the process of sanctification and renewal of the mind allow Christians small glimpses of heaven on earth. What a joy to have the ability to break the bondage of a worldly and tainted thought life and experience the peace that surpasses all understanding.