Why do I always end up liking my friends?

First I'll become friends with a girl and I'll be cool with just being friends with them. After awhile of talking to em and hanging out though I realize that I like them. It sucks because I don't wanna ruin a friendship and because whenever I like a girl I fall for her really hard. So that means she is mostly what I think about. It happens almost every time and I know it's a bad situation to keep getting into but I don't know what to do to either keep it from happening or otherwise
Why do I always end up liking my friends?
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