Has anyone else been in a situationship/casual situation that destroyed their self-esteem?

I thought that I was seeing this guy and it was going to lead to something. Meanwhile, he had a girlfriend the entire time. This mentally destroyed me because, I was like “why her and not me?”, “what does she have that I don’t?”, “what is so terrible about me that you wouldn’t take me seriously?”.
Has anyone else been in a situationship/casual situation that destroyed their self-esteem?
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