It was evening. The sun was below the horizon; but his rosy beams yet illuminated a feathery cloud, that floated high above the world. I arose, I reached the cloud; and, throwing myself upon it, floated with it in sight of the sinking sun. He sank, and the cloud grew gray; but the grayness touched not my heart. It carried its rose-hue within; for now I could love without needing to be loved again. The moon came gliding up with all the past in her wan face. She changed my couch into a ghostly pallor, and threw all the earth below as to the bottom of a pale sea of dreams. But she could not make me sad. I knew now, that it is by loving, and not by being loved, that one can come nearest the soul of another; yea, that, where two love, it is the loving of each other, and not the being loved by each other, that originates and perfects and assures their blessedness. I knew that love gives to him that loveth, power over any soul beloved, even if that soul know him not, bringing him inwardly close to that spirit; a power that cannot be but for good; for in proportion as selfishness intrudes, the love ceases, and the power which springs therefrom dies. Yet all love will, one day, meet with its return. All true love will, one day, behold its own image in the eyes of the beloved, and be humbly glad. This is possible in the realms of lofty Death. "Ah! my friends," thought I, "how I will tend you, and wait upon you, and haunt you with my love."This is a beautiful passage and the part that really struck me is how he speaks of the power that comes to someone who loves another. As he says, this is a power that cannot be but for good. I would call it (somewhat tritely) a "power under your beloved" rather than a "power over" them. It is a power, but it's a power to serve, honor and lift up that person; not to manipulate them to do anything for you (selfishness, using them to serve or satisfy you) but a power to do good in their life.
It is a position of sacrificing your own interests, taking up their interests and doing what you can to see them blessed. But the true mystery is that it really does give you power in their life. This is something that I have experienced with 2-3 of my closest friends and it's hard to explain but I really feel like I have the ability to affect their lives in various ways, such as influencing their thoughts, emotions or decisions.
Like Macdonald says, this doesn't have anything to do with whether that person even knows you. Anybody (loving or not) can manipulate others through words, to change how they act. I'm not talking about giving advice to my friends who trust me and therefore I have power in that trust. What I'm talking about is that through my love for them, I have a direct line of power into their spirit/soul to change them and bless them.
But lest anyone fear manipulation, the other mystery is that this power is purely derived from the love (selfless concern for the other), so if a person even starts thinking about using that power for anything but the good of the beloved, the power fades.
A more concrete example I thought of is this. When I was in college, I remember once when my campus minister was sharing some prophetic words with me and a few other students there. These were not "regular" prophetic words, but rather he was getting prophetic insight into our lives because he was our minister. On other occasions, he would just randomly know stuff about me. I believe he was able to do this because he had true spiritual authority over our lives, but at a deeper level you can only have spiritual authority over another person if you love them. Jesus says the greatest among you will be the servant of all. True love is laying down your life for your friend. Therefore the path to gaining spiritual authority over others is to have selfless love for them, considering your own personal interests as less important than theirs.
And on a slight tangent, this is how you can reliably identify spiritual authorities over you. There is a lot of confused and confusing teaching about authority in the church, but at a simple level if you want to know if someone is an authority over you, just ask yourself how much they love you. The proportion in which they selflessly love you is how much of an authority they are.