There are several really great realizations I had (and continue to have) once I grew into myself and developed a substantial understanding of who I am.
First, I realized that when I thought I knew myself in younger years, I had only a vague, fumbling sense, which is comforting when I think about all the mistakes I've made and situations I would now have handled differently. Poor young me, she was really doing her best, and older, wiser me knows that - and is grateful for the mistakes that helped fuel my progression. This also means that when even older, wiser me of the future looks back at me now, she will likely also be understanding and grateful.
The next realization is one of my favorites, and it's that growing into yourself is far more gratifying than growing up in the traditional sense, and more than that, it's not a destination nearly as much as it is a journey. To me, growing up indicates a climb, peak, and plateau, whereas I think of growing into yourself as perpetual. Growing into yourself develops an increasingly instinctual internal compass, and this is probably the most crucial sense of direction you can possess.
Next, knowing who I am made me appreciate and understand myself on a different level, and recognize that happiness, progression, and success can only be achieved when I'm being true to myself. This eliminated any ounce of desire to a) try to act like someone I'm not, and b) to be around anyone who makes me feel inclined to do so. There are too many things to do, too many people to connect with, too many revelations to be had, too many moments to be savored, and too much self-reflection to engage in to waste any time or energy on facade. (Sidenote: I don't think this means that people who make you feel you should be someone else are inherently not good people, it just means they're not good for you, that you guys don't move on the same wavelength and don't intrinsically click. I like this because it makes you deeply appreciate the people with whom you do.) Plus, as someone who values the people in my life above all else, I know that you cannot build meaningful relationships unless both people are truly being themselves.
Finally, continuously learning myself has helped me figure out what really matters to me, and it made me realize that in what is ultimately a rather brief and fleeting time on earth, you have to cultivate and protect your happiness. I love happiness for its own sake, and because I think it's healthy and beautiful and contagious and necessary in a world too often burdened by sorrow, but also because in being happy now, I can reflect back on times when I was less happy, and the difference in how I moved through the world is drastic. Happiness helps breed confidence, resilience, inspiration, motivation, compassion, and so much more - all stuff this planet needs more of, and that compel people to contribute to the betterment of the world and the lives of those around them.
All this to say, once you know yourself you have to treat yourself with the same care, respect and love you would show anyone else you value. It's hard to remember this sometimes because our relationship with ourselves is the only one where we're on the inside looking out, so seeing yourself must be a deliberate decision.
So every once in a while, make that decision and remind yourself to have your own back. Then crank a song that hits you in the depths of your soul, and step out into the world to continue glowing and growing like only you can.