tl, dr; The Rosenhan experiment had eight sane people gain secret admission to 12 different hospitals by claiming to hear voices. Immediately on admission, they stopped claiming to hear voices, and requested release. Although fellow patients were quick to accuse participants of 'being sane', journalists, or professors (on account of their note taking), hospital staff uniformly failed to recognize their sanity.
The corollary "note-to-self" is to avoid doing anything that would land oneself in a mental institution!