From Aleteia:
St. Vincent de Paul, in his Introduction to the Devout Life, explains this central spiritual principle.
A lively appreciation of the grace given to you should make you humble, for appreciation begets gratitude .. .Any one who will calmly consider what he has done without God, cannot fail to realize that what he does with God is no merit of his own; and so we may rejoice in that which is good in us, and take pleasure in the fact, but we shall give all the glory to God Alone, Who Alone is its Author.