Perfection of love implies the removal or extinction of all selfishness. In other words, perfect love is always PURE love. We may probably conceive of love, which is pure in its nature; but is deficient, and therefore not perfect in its degree or intensity. But we cannot conceive of love which is acceptable to God, and is perfect in degree, which has any intermixture of selfishness.
Perfection of love is necessarily relative to the capacity of the subject of it. In other words, what would be perfection of love in one would not be in another, whose capacity of loving is greater. That precise amount or degree of love in man, which would be characterized as perfect in consequence of being all his capacity could render, would be imperfect in an angel or other being of greater capacity.
— edited from The Interior or Hidden Life (1844) Part 1, Chapter 17.