Pain and love

I guess a fundamental question I have never settled with it whether or not part of love is pain? Maslow has said that the opposite of love is not hate but rather apathy, non feeling. So it begs the question of what exactly is involved in love, what it can encompass, and what can never be a part of it. Human love that is, since divine love is perfect. Human love seems flawed, always, but does this necessitate pain. The colloquial saying -no pain no gain seems to suggest it does. If love is an experience for growth then pain must be a part of it. Pain from the lost of one's self. Despite the treasure of love, loving another involves sacrifice. Sacrifice of autonomy. The ability to come and go or even think as one pleases is altered. If one wants to travel but is in love do one's plans get changed? If one has a conviction but your love doesn't see eye to eye, does one's thoughts changed. If  one's tired of talking but love wants to engage, do you speak?
And what is hoped for as one goes through the pain of love, the lost of self, union? But why, why is the human is constant conflict? Wanting to be completely taken over by another and yet wanting to be by one's self. Maybe it is in relationship to the first split be with God, fully with God. No thought to the question of -who is your Lord? Just complete submission, knowing without thinking. Oneness without separation, but on the fateful split and man exile from the garden, that choice, that separation of what God wants and what man wants. Autonomy, freedom of choice and yet we find in this a burden and many of us go on the path longing for union again, complete submission again. Union.
And we resemble this in our human relationships. Wanting to be a part and completely submits to the will of our love and completely wanting to run away in autonomy -to do things our way. It seems love requires some kind of pain. True requires some kind of sacrifice.