All of our relationships exist for a single beautiful purpose that expresses itself in two different ways. First, everyone and everything is in our life to help us grow; to provide just the conditions we need to become that better, truer person just waiting to be brought forth. But the other and equally important half of this same purpose and promise - without which the first part can't be realized - is as follows: everyone and everything is also there in our life to help us see everything in us that now stands in the way of our realizing this same higher possibility.
Love's immeasurable gift, for those who will open the door to receive it, is a whole new understanding that changes not just the meaning of what we see - and react to - in others, but that also changes how we respond to what others reveal to us... about ourselves.
Relationships reveal us to ourselves because they are "mirrors," reflecting back to us qualities light and dark, high and low, some delightful and others self-compromising and self-limiting. Our relationships become "magical" as we realize that whatever remains concealed within us can't be healed, and that our partner - our "mirror" in each moment - is actually the agent of these revelations that alone can release us from our limitation.
Yes, of course, the limits of our patience, kindness, or ability to forgive will be tested. How else would we ever come to realize the present limits of our capacity to love... so that as grows our willingness to recognize the secret good in unwanted revelations, so does our ability to see - and to appreciate others - for what they are in reality: an "agent" of love whose secret mission is, in part, to initiate the kind of healing that begins with revealing whatever painful character still lives concealed within us.