Unrequited Love. Any advice welcomed please.?

Hello folks, this is my first question; I normally advise others.

I recently fell deeply 'in love' with an attached lady. For the first time in my life I declared my secret love for someone, just in the hope she felt the same.

I am very certain she liked me, certain she was fond of me aswell. Quite sure she found me sexually attractive. I too felt all these things for her, but also really care(d) for her. Indeed I still worry about her and often cry rather than be elated. Yet she has displayed absolutely no caring about nor for me, plus no hint of wanting to be just friends. I stopped chasing her and asked to be her platonic friend instead, as it was obvious she loved the other man.

I can understand when the other person doesn't find someone attractive, but how can one person truely care for someone but it's not recipricated.

Any thoughts please?

Thanks.