Oh boy. Just one?

I guess I'd go with "signing up to a random online forum back in 2012".

I was a very shy and introverted kid back then, without friends or social life to speak of. I would spend all my time playing videogames and reading books.

That online forum gave me a chance to speak to other people while staying "safe" in my shell. Without realising it, I slowly gained confidence and social skills that helped me make friends both online and irl, some of whom I still speak with to to this day. Thanks to one of the people I knew on that forum, I now have a job that I like.

I wouldn't recommend online forums nowadays to fight depression/lack of social skills, as the internet has become a cesspool. Online chats are breeding grounds for political extremists. But in my case it definitely helped.

A close second would be having a girl in college confessing to me. I had never really thought about my sexuality back then: it just wasn't on my mind, like, ever (which should've been a red flag, but whatever). She was really nice and wasn't pushy at all, but I knew that I couldn't leave her hanging forever, and I had to give her an honest answer in a relatively short time.

Well, long story short, I realized I wasn't straight. At first I thought I was bi, then gay, but a few years later I understood that I am ace (again, should've been obvious by the fact that I literally never thought about sex for the entirety of my teenage years, but I'm dumb).

But seriously, there are so many important moments in one's life, it's difficult to choose only one or two. Watching nature documentaries with my brother as a kid turned me into a huge animal lover, to the point that I'm literally unable to kill a fly because it makes me sick. Thanks bro, those are some of my most treasured memories!