Well, the last crush I had was during my first year pursuing an MA. The guy was smart, intelligent, funny, and kind of had the same attractiveness as James Franco. I mistook his kindness for flirting (although it didn't help when we both worked as temporary English instructors for Korean exchange students and we chaperoned trips together. When we went to Disneyland, he said I'd make a good Princess Jasmine, and when we went to Hollywood, our students kept asking us if we were boyfriend and girlfriend). I never acted on my feelings, because 1) I had a feeling I was overanalyzing his behavior, 2) I found out that I was correct about that, and 3) he had a girlfriend and I never want to be that person that disregards the feelings of someone else for my own personal happiness. I wouldn't want someone flirting with someone I date, so I am not going to do that to someone else.
I got over him relatively quickly, but I think that might be because I'm a little older. When you're younger, your crush not returning your feelings can seem like the end of the world, but you eventually get over it.