Quoted from his first book https://en.wikipedia.org/wiki/Success_and_Failure_Based_on_Reason_and_Reality, "Success and Failure Based on Reason and Reality" https://www.amazon.co.uk/SUCCESS-FAILURE-BASED-REASON-REALITY/dp/9970983903/ on Amazon, P.58 (July 2018)
Related quotes
Many sources attribute this quote to Brown without giving a specific reference to her writings. The earliest located is the following variation from p. 47 of Musgrave Landing: Musings on the Writing Life by Susan Musgrave (1994), which Musgrave quotes as "Rita Mae Brown's warning": "If you become the kind of writer who calls forth heated emotional states, be careful. There are a lot of unbalanced people out there. The statistics on insanity are that one out of every four people is suffering from some form of mental illness. Think of your three best friends. If they're okay, then it's got to be you."
Disputed
“It's okay to love someone who doesn't love you back, as long as they're worth loving.”
Variant: It's all right to love someone who doesn't love you back, as long as they're worth you loving them. As long as they deserve it.
Source: Clockwork Angel
Source: The Analects, Other chapters
Source: https://notjustok.com/article/interviews/simi-in-conversation-with-notjustok-for-womens-history-month/ Simi on an interview during Women History Month
I Can't Turn You Loose (1965).
Song lyrics