Accepting that I was an introvert. I remember the exact moment: I was traveling, had just settled down with a good book at a hostel, and then heard some folks heading to the bar. I remember thinking "gosh, I should be social," and then "nah, I'd rather be here." Self acceptance of that was a big change for me.
A thing I've learned on top of that is that people can interpret the lack of care about social functions to be lazyness or harshness. Even introverts can enjoy certain social functions if they become more accustomed to take the edge off. I say this myself as an introvert - staying home all the time and fulfilling ones' comforts often makes one their own worst enemy when it comes to fulfillment. Comfort makes one weak. I should know, I regret being my own best servant of solitude. Be better than me. Push yourself outside of the meager boundaries of who we think we are. Or we can never be great, legendary.