You knew all my intimate thoughts and cleared up all my doubts. I once told you how astonished I was that God does not give equal glory in heaven to all His chosen. I was afraid they were not at all equally happy. You made me bring Daddy’s tumbler and put it by the side of my thimble. You filled them both with water and asked me which was fuller. I told you they were both full to the brim and that it was impossible to put more water in them than they could hold. And so, Mother darling, you made me understand that in heaven God will give His chosen their fitting glory and that the last will have no reason to envy the first. By such means, you made me understand the most sublime mysteries and gave my soul its essential food. —St. Thérèse of Lisieux, The Story of a Soul. (New York: Double Day, 2001) 20.
You can find some quotes here. Or read the full Story of the Soul. It is very good.