Canonical version
To Mrs Smith, a new Bahá’í, who belonged to a distinguished Philadelphia family
To Mrs Smith, a new Bahá’í, who belonged to a distinguished Philadelphia family and who was suffering with a headache, the Master said, ‘You must be happy always. You must be counted among the people of joy and happiness and must be adorned with divine morals. In a large measure happiness keeps our health while depression of spirit begets diseases. The substance of eternal happiness is spirituality and divine morality, which has no sorrow to follow it.’
Source: Honnold, Annamarie, Vignettes from the Life of ‘Abdu’l-Bahá, p. 129
Collected from bahaistories.com (Subject: happiness).