St. Faustina
“On the initial day of the retreat, I was visited by one of the sisters who had come to make her perpetual vows. She confided to me that she had no trust in God and became discouraged at every little thing. I answered her, ‘It is well that you have told me this, Sister; I will pray for you.’ And I spoke a few words to her about how much distrust hurts the Lord Jesus, especially distrust on the part of a chosen soul. She told me that, beginning with her perpetual vows, she would practice trust. Now I know that even [some] souls that are chosen and well-advanced in the religious life or the spiritual life do not have the courage to entrust themselves completely to God. And this is so because few souls know the unfathomable mercy of God and His great goodness.”
Source: St. Faustina, Diary: Divine Mercy in My Soul