Anne Morrow Lindbergh said this quote

If one sets aside timefor a business appointment, a trip to the hairdresser, a social engagement or a shopping expedition,that time is accepted as inviolable. But if one says: I cannot come because that is my hour to be alone,one is considered rude, egotistical or strange. What a commentary on our civilization, when beingalone is considered suspect; when one has to apologize for it, make excuses, hide the fact that onepractices it—like a secret vice!