Since you have tagged your question with both Robert Fulghum and Santha Rama Rau's names, and placed the question in "Literature," I am assuming that you are looking for literature based quotations which speak to character and self-identity which come from literature.
Since you named two very specific authors, I will provide quotes by them first.
Provided in his novel All I Really Need to Know I Learned in Kindergarten, Robert Fulghum provides the following ideas which help to establish one's identity (in regards to making him or her a good person).
"To be fair, we must share" (5). While the quote seems relatively straight forward, it means much more "underneath." To be a good person, to help to make us who we are, we must decide to share or not. With this decision, we decide what kind of person we are going to be.
When looking for a quote by Santha Rama Rau on identity, this is the one quote I felt spoke directly to character: “Really, in the end, the only thing that can make you a writer is the person that you are, the intensity of your feeling, the honesty of your vision, the unsentimental acknowledgment of the endless interest of the life around and within you. Virtually nobody can help you deliberately — many people will help you unintentionally.” Once again, it is necessary to look beneath what the quotes "says." Here, Rau is highlighting the importance of honesty and intensity. To find one's true identity, he or she must be honest with who they are and be intense in their desire to find himself or herself.
As for other literary quotes which speak to identity, here are some popular ones.
Emily Dickinson: "I'm Nobody! Who are you? / Are you--Nobody --Too?"
Oscar Wilde: "Most people are other people."
Charlotte Bronte (Jane Eyre): "I am a free human being with an independent will.”
William Shakespeare: “We know what we are, but not what we may be.”