How do I stop myself from falling in love with someone I can't have?

Unrequited love, something I've struggled with my entire life. This time I'm becoming obsessed(I guess obsession is quite different than love) with a celebrity-Anna Kendrick. It's been happening for the past year or two, on and off with her. I know I can't possibly have her and will probably never even have the honor of talking to her face to face. My question is, how the heck do I stop myself from falling in love with her? How do I get over her?