From St. Therese of Lisieux, Story of a Soul, Ch. 1:
I often asked myself why God had preferences, why all souls did not receive an equal measure of grace. I was filled with wonder when I saw extraordinary favours showered on great sinners like St. Paul, St. Augustine, St. Mary Magdalen, and many others, whom He forced, so to speak, to receive His grace. In reading the lives of the Saints I was surprised to see that there were certain privileged souls, whom Our Lord favoured from the cradle to the grave, allowing no obstacle in their path which might keep them from mounting towards Him, permitting no sin to soil the spotless brightness of their baptismal robe. And again it puzzled me why so many poor savages should die without having even heard the name of God.
Our Lord has deigned to explain this mystery to me. He showed me the book of nature, and I understood that every flower created by Him is beautiful, that the brilliance of the rose and the whiteness of the lily do not lessen the perfume of the violet or the sweet simplicity of the daisy. I understood that if all the lowly flowers wished to be roses, nature would lose its springtide beauty, and the fields would no longer be enamelled with lovely hues. And so it is in the world of souls, Our Lord's living garden. He has been pleased to create great Saints who may be compared to the lily and the rose, but He has also created lesser ones, who must be content to be daisies or simple violets flowering at His Feet, and whose mission it is to gladden His Divine Eyes when He deigns to look down on them. And the more gladly they do His Will the greater is their perfection.
I understood this also, that God's Love is made manifest as well in a simple soul which does not resist His grace as in one more highly endowed. In fact, the characteristic of love being self-abasement, if all souls resembled the holy Doctors who have illuminated the Church, it seems that God in coming to them would not stoop low enough. But He has created the little child, who knows nothing and can but utter feeble cries, and the poor savage who has only the natural law to guide him, and it is to their hearts that He deigns to stoop. These are the field flowers whose simplicity charms Him; and by His condescension to them Our Saviour shows His infinite greatness. As the sun shines both on the cedar and on the floweret, so the Divine Sun illumines every soul, great and small, and all correspond to His care—just as in nature the seasons are so disposed that on the appointed day the humblest daisy shall unfold its petals.