Turn to any page of St. Faustina’s Diary, and you’ll find spiritual gems. Like this one:

When I was close to the Lord, He said to me, “Why are you afraid to begin the work which I have commanded you to carry out?” I answered, "Why do You leave me on my own at such times, Jesus, and why do I not feel Your presence?” [He replied], “My daughter, even though you do not perceive Me in the most secret depths of your heart, you still cannot say that I am not there. ... My daughter, know without doubt, and once and for all, that only mortal sin drives Me out of a soul, and nothing else (Diary, 1181).