"Be yourself; everyone else is already taken" a famous quote by Oscar Wilde, is a call to authenticity, urging individuals to embrace their unique identity, quirks, and talents rather than imitating others. It means that because everyone else's identity is already occupied, trying to be someone else is a futile, unoriginal, and exhausting endeavor.
It's a reminder to embrace your own qualities and be true to yourself, without trying to conform to others or be a replica of someone else.
- From online with editing
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Two thoughts came to me, when I stumbled upon this interesting quote this morning:
1. It's very similar to "To Thine Own Self Be True" as said by Shakespare in his play "Hamlet"
2. Oscar Wilde himself was a very colourful, witty and somewhat flamboyant person
Also I don't think it means we shouldn't learn from others, but learning ain't copying 
Below is an interesting and very relevant (especially in the virtual worlds) statement from an anonymous person in Quora:
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Some people argue that to “be yourself” means to not care what other people think, those people are wrong and are not being themselves because “being yourself” is not about a relation with other people, it's about a relation with yourself.
Be yourself means: don’t try to pretend you are rich, you have tastes you don’t have, you have everything handled when you don’t have, you are better at something than you actually are, you have hobbies you don’t actually have, you have skills you don’t actually have, you have a status you don’t actually have, and so on.
It's not about not saying or doing less, it's about not saying or doing more. You can be a generally honest person and not tell your life story to every single person you meet, that doesn't make you less honest, just private.
Being yourself means not being socially fake. Being fake means pretending you are more than you are. Being fake is tiring, when you pretend you're something you're not you don't feel good, you do it because you have to. When you behave in a certain way to make someone like you, you don't do it because you feel like doing it.
I cannot be perfect and I don't want to, the people who love me know I have a good natured soul, and that's enough for me. The world is good-natured to people who are good natured.
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Well said! And enough soul searching for one day 
