“Three things destroy a man: considering his own deeds to be really great, forgetting the sins that have been committed, considering his own opinion to be the highest.”
Al Khisaal. vol.1, p. 112
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Muhammad al-Baqir 30
fifth of the Twelve Shia Imams 677–733Related quotes

The Ethics of Belief (1877), The Weight Of Authority
Context: It is hardly in human nature that a man should quite accurately gauge the limits of his own insight; but it is the duty of those who profit by his work to consider carefully where he may have been carried beyond it. If we must needs embalm his possible errors along with his solid achievements, and use his authority as an excuse for believing what he cannot have known, we make of his goodness an occasion to sin.

[Ghatak, Ritwik, Cinema and I, 1987, Ritwik Memorial Trust, 65]
“Every man has his own reason for every deed. Usually it is selfish.”
Source: Drenai series, Quest for Lost Heroes, Ch. 10

“Every man has a right to his own opinion, but no man has a right to be wrong in his facts.”
Deming Headlight (New Mexico), 6 January 1950, as cited in the Yale Book of Modern Proverbs and at There Are Opinions, And Then There Are Facts; Freakonomics blog post by Fred R. Shapiro http://www.freakonomics.com/2011/08/18/there-are-opinions-and-then-there-are-facts/ (18 August 2011)

Why Can't A Man Stand Alone?
Song lyrics, All This Useless Beauty (1996)
Source: Dictionary of Burning Words of Brilliant Writers (1895), p. 9.