A second mark of perfect love to God is the existence of a desire to promote his glory, which is the other higher and more decisive characteristic of this complex mental state, in such a degree, that we are not conscious of having any desire or will at variance with the will of God.
In other words, it is our sincere and constant desire to do and suffer in all things the will of God. When such is the case, when there is an entire and cordial acquiescence of our own in the will of God both to do and to suffer, we have the second mark, and we may add also, the most important and satisfactory one, that our love is perfect. The nature of the human mind is such, that we never can have an entire and cordial acquiescence in the will of God in all things, without an antecedent approval of and complacency in his character and administration.— Accordingly the second mark, viz, a will entirely accordant with and lost in the will of God, is of itself sufficient, inasmuch as it necessarily includes and embraces the first. And by this mark alone, as I suppose, we might know, whether our love is or is not perfect.
— edited from The Interior or Hidden Life (1844) Part 1, Chapter 17.