55% sureLots of sources credit Anaïs Nin with this, and they agree with each other. The book or the speech it first came from hasn't turned up yet.
What turned up
Listed in Wikiquote's sourced section for The Diary of Anaïs Nin, Vol. 2 (1934-1939, pub. 1967), no entry date given; the diary-page context (whose voice speaks the line) is unconfirmed against the primary — held at likely per confirm-the-speaker.
Work
The Diary of Anaïs Nin, Vol. 2 (1934-1939)
Occasion
1934-1939 · a diary reflection on the limits of rescuing the people you love
Sources checked
en.wikiquote.orgChecked using claude-fable-5, 22 August 2026Wikiquote sourced Vol. 2 section, undated entry. GAP: diaries record other people's words too — the surrounding passage has not been read (Vol. 2 is lending-restricted), so the speaker check stays open. Raise only after the primary page is read.