How I came to the realization that eros was different from agape? Or something else?

I assume most people understand the difference conceptually but not necessarily at a visceral level. At least that was the case with me for a long time. I guess my story starts with a long distance relationship with someone I "loved" (though in retrospect it was clearly about sex): I made certain life decisions to allow us to live in the same geographic area (there were a few other considerations so I wouldn't say plainly that I relocated to be with him). Pretty much as soon as I was settled in my new environs he dumped me. I was devastated (there some other things going on at the time, e.g. my mother's sudden health catastrophe). I fumbled around dating for a year until I met a man around whom I was pretty guarded but still willing to cautiously explore possibilities. He ultimately proved his commitment in how he dealt with my mother's passing. At that time there was a very fundamental shift internally in how I perceived love and commitment. I relaxed my guard around him and we are still together 8 years later. No regrets at all. As he recently commented, "there's no one else I'd rather be in lockdown with" and I agree.

I'm not sure if I answered your question. It wasn't a cognitive process, it was more fundamental than that.