Oh man, this thread brought me back to my worst oneitis ever, with this girl for 1,5 yr back in 2013-2014.
In my eyes she was the most beautiful creature in the whole universe, I absolutely loved her. I managed to make her my gf, but, as usually in these situations, I became too attached, got needy, jealous, emotional and all that ****.
She went to spend a semester abroad, and of course broke up with me. I was devastated, and could not get her out of my mind. It was like a powerful spell. Looking back, I am like "WTF was I thinking..?"
I initiated NC, but still was not fully over her when she came back from abroad months later. I accidentally came across her at some point, and felt horrible. As if something broke inside me.
I only was really able to get over her when I moved to the US and never saw her again. This experience taught me to take stuff like in this forum seriously and to take care of myself etc. In retrospect, I needed it. But man, was it hard...
I am sure more or less we all have at least one such story to share, from our "previous" sevles.