'Three months have passed since I first saw the Cossack girl, Maryanka. The views and prejudices of the world I had left were still fresh in me. I did not then believe that I could love that woman. I delighted in her beauty just as I delighted in the beauty of the mountains and the sky, nor could I help delighting in her, for she is as beautiful as they. I found that the sight of her beauty had become a necessity of my life and I began asking myself whether I did not love her. But I could find nothing within myself at all like love as I had imagined it to be. Mine was not the restlessness of loneliness and desire for marriage, nor was it platonic, still less a carnal love such as I have experienced. I needed only to see her, to hear her, to know that she was near--and if I was not happy, I was at peace.I think that rings true for at least any male that has ever been in love. No idea how it works for a woman -- is there a female writer with the kind of insight of Tolstoy? Could I understand it if there was?
The character "writing the letter" is a wealthy Russian noble, somewhat "looking for his head" in the military -- it seems that his heart found him first.