The most sublime grace: transformation into God through charity

"Ordinary graces make up the essential factor in the development of the spiritual life right up to its full maturity. Passive purifications and the partial progressive transformations, which mark the development of the soul, are ordinary graces, that is to say, normal and to be expected in the process of sanctification. From this point of view, the most sublime grace, of transformation into God through charity, remains an ordinary grace.

Those graces can be called extraordinary which, strictly speaking, are not necessary, because they do not concern the substance of the soul's progress. You could call them accessories. They are useful helps for its growth, acting sometimes like signposts or messages which bear a mission, or exist at other times in order to encourage the soul in its simple ascent or, again, to bring it acknowledgement in the eyes of the people of God. In the past, attention was focused almost entirely upon this kind of grace, especially when it assumed perceptible mnifestations, that is to say everything which is understood by mystical phenomena, such as visions, locutions, levitations, etc."

-- Thérèse, The Little Child of God's Mercy by Angel de les Gavarres