Restlessness

I really feel i ve deeply fallen in love with my best friends’ sister. She doesnt seem to have the same feelings though. There is a strong sense of guilt deep in my heart regarding this. I somehow am not being able to get over it. I keep thinking about her always and sulk at my ill fate that she
happens to be my best friends’ sister. I know that keeping such feelings for her is bad for me. I just want to get over it and forget her. can i have some advice please??