• I had an epiphany when one of the students told me that she knew that I hated her and that she hated me, and asked me if I would do something for her. This was someone who I liked. This was the first indication that I didn't understand other students at school. That made me start trying to pretend, to fit in in class, to at least some degree. Before that I didn't know.
• Later, I had an epiphany that the other students were interacting with each other outside of school even though I wasn't, and it made me realize that I was basically asocial and that the difference I had perceived was much greater than I had ever perceived. After that, I made an attempt to be social in class, for the first time ever.
• As an adult, I had an epiphany upon finding out that I'm autistic. It made me understand so many aspects of things, like my sensory problems and why other people always thought I was different. I used that information to teach myself how to get a job, whereas before I had no idea.
• Years later, I had an epiphany when speaking with someone who is both autistic and transgender, and it made me realize that while I knew that I'd spent most of my life trying to fit in by at least some small degree, there was a huge aspect of that that related to gender, that I had always been trying to portray just neutral, not a strong example of my assigned gender, but just neutral, that neutral was just about the closest I could conceive of, that I had literally no concept of what it was like to be anyone else of my assigned gender, and that I hadn't even ever attempted to. I realized why I had always thought it would have been easier if I had been born someone of the opposite sex, and(Since I'd had depression, it was common for me to wish to die to be reincarnated as someone else.) why my dreams of death and reincarnation were always of someone of the opposite sex. And then I realized that I didn't think I had ever tried to make friends of the gender I was assigned. I went through my whole life and tried to find examples of people of my same sex who I'd made anything more than the slightest effort to interact with, and I found no good examples. And I suddenly realized why I always imagined myself as opposite-sex characters in books and movies, and why all of my daydreams were as someone of the opposite sex. And the fact that my fantasies involved me as the opposite sex suddenly seemed more relevant than just strange now(I was obviously not the most astute observer of my own social development). I thought about this for weeks, trying to find some hint of behavior similar to my assigned gender, and I found very little, almost nothing, really. I hadn't realized exactly how much effort I had spent trying to not be conspicuous that I hadn't realized a major part of what I was hiding.

So yes, I have had several such instances. There are a few more, but those are the most significant ones I can think of right now.