St. Faustina
“On a certain occasion, the Lord said to me, ‘I am more deeply wounded by the small imperfections of chosen souls than by the sins of those living in the world.’ It made me very sad that chosen souls make Jesus suffer, and Jesus told me, ‘These little imperfections are not all. I will reveal to you a secret of My heart: what I suffer from chosen souls. Ingratitude in return for so many graces is My Hearts constant food, on the part of [such] a chosen soul. Their love is lukewarm, and My Heart cannot bear it; these souls force Me to reject them.'”
Source: St. Faustina, Diary: Divine Mercy in My Soul