It works the other way around too. I think it's just when someone in general that you're interested in is in a relationship, something kicks in, feelings of some sort, who knows. Makes you do some stupid things, things you didn't expect yourself to do in hopes to get them for yourself. Happened multiple times to me, I never gave too many thoughts on it though. I do know the one thing I was always complimented on (or hated on at times) aside my eyes was my attitude, saying that even in the worst of times, times they expected me to fall to my knees, or dark times for themselves, I would always find the brighter side of things, always optimistic. I noticed a lot of girls for some reason liked that, despite people saying girls like the bad guys.
As far as relationships went, never had an issue having one, had many attempt to destroy my relationship with another for themselves, pretty messed up girls out there... However, like I said, I was disconnected from them, didn't pay attention to it. However, there was this one girl, Abbie, she was amazing. She was like a little sister to me, 3 years younger, and I thought of her as even my best friend, which to me means a lot considering my best friends are the world to me, so much so that when I got into a fatal accident in Hawaii and was hospitalized, they all took time off from school and work to fly out and stayed there till I woke up, so I do take a title of best friend seriously, as best friends are more of family than normal friends. But aside the point, she became a best friend in my view, someone I always wanted in my life through thick and thin.
Well one day, I broke up with my girlfriend at the time, at the same time, Abbie found interest in the guy so I was urging her to ask him out, thinking it would be good for her since she never had a boyfriend before. I have to say, it was quite entertaining too. Well, she went to go ask him out while I sat at a table with her close friend, Val, when Val just looked at me and said I had to be the most stupid human on the planet, so mean! Laughing I asked why, she said Abbie had a crush on me for years and never asked me out since I always had a girlfriend. Again, I shrugged it off, or tried to this time... Kept thinking about Abbie now, how I tried to get her to hook up with some other guy, thought what that guy had that I didn't, blah blah, things rushing through my head. After 2-3 days, I finally realized I was jealous, I liked Abbie more than just a friend, and I screwed up big time getting her to ask this guy out because they already went on a date by now. So despite the fact I knew she went on a date and probably wants to go on more with the guy, I had to ask anyway.
I don't know if it was because I found out she liked me, or if it was because she was entering a relationship, but something changed the way my mind worked for those few days, something was making me do something I might regret or find stupid. All I knew at that time was if I didn't try then and there, she may have chosen the other guy permanently over me, which I simply couldn't imagine.