Vanity
A visual of “vain”, from LiberalDictionary.com, in reference to one who is excessively proud of their appearance, qualities, or “achievements” (see: Buss study) or “accomplishments; ineffectual or unsuccessful; senseless or futile; without real significance, value, or importance; baseless or worthless; without effect or avail; to no purpose; given to ostentatious display, especially of one’s perceived beauty. [2]
In terminology, vanity, from the Latin vanus “empty, void”, refers to something that has no real value; a thing that is empty or valueless; inflated pride in one’s own appearance; possibly from the PIE root eue- “to leave, abandon, give out”. [1]

Quotes
The following are related quotes:

“Nothing happens in vain, but everything from reason and by necessity.”
Leucippus (c.460BC), On Mind (Fragment L1)

“The [Faustian] puppet-play echoed and vibrated in many tones through my mind. I, also, had gone from one branch of knowledge to another, and was early enough convinced of the vanity of all. I had tried life in many forms, and the experience had left me only the more unsatisfied and worried. I now carried these thoughts about with me, and indulged myself in them, in lonely hours, but without committing anything to writing. Most of all, I concealed from Herder my mystic-cabalistic chemistry, and everything connected with it.”
Johann Goethe (1770), reflection on intercourse with Johann Herder, in Strasburg [3]

See also
Alley equation
Beckhap’s law
Buss study
Drive-thru paradox

References
1. (a) Vanity – Merriam-Webster.
(b) Vain – EtymOnline.com.
2. Vain – LiberalDictionary.com.
3. (a) Goethe, Johann. (1811-1833). From My Life: Poetry and Truth. Publisher
(b) Goethe, Johann. (1832). Faust (translator: Bayard Taylor) (pgs. 230-31). Houghton, Mifflin & Co., 1883.

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