“Comparison is the thief of joy.”
As quoted in Becoming a Great School (2013) by Cooper, Gustafson and Salah, p. ix
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Theodore Roosevelt 445
American politician, 26th president of the United States 1858–1919Related quotes

“Set a thief to catch a thief.”
Epigram 43; translation by Robert Allason Furness, from Poems of Callimachus (1931), p. 103
Epigrams

“4106. Set a Thief to catch a Thief.”
Introductio ad prudentiam: Part II (1727), Gnomologia (1732)

“4788. The Thief is sorry he is to be hanged, but not that he is a Thief.”
Introductio ad prudentiam: Part II (1727), Gnomologia (1732)

“The petty thief is imprisoned but the big thief becomes a feudal lord.”
Source: The Complete Works of Chuang Tzu

“Do not despair: one thief was saved. Do not presume: one thief was damned.”
Attributed to St. Augustine in The Repentance of Robert Greene, Master of Arts http://www.oxford-shakespeare.com/Greene/Repentance_Robert_Greene.pdf (1592) by Robert Greene.
Disputed
Variant: Do not despair; one of the thieves was saved. Do not presume; one of the thieves was damned.

“Once a thief, always a thief, only now I steal from the enemy.”
Sharpe (Novel Series), Sharpe's Escape (2003)
Context: Until two days ago,' she went on suddenly, 'I thought that my life depended on other people. On employers. Now I think it depends on me. You taught me that. But I still need money.'
'Money's easy,' said Sharpe dismissively.
'That is not the conventional wisdom,' Sarah said drily.
'Steal the stuff,' Sharpe said.
'You were really a thief?'
'Still am. Once a thief, always a thief, only now I steal from the enemy. And some day I'll have enough to stop me from doing it and then I'll have to stop others from thieving from me.'
'You have a simple view of life.'
'You're born, you survive, you die,' Sharpe said. 'What's hard about that?
“Even if he was a thief, he was my thief. I could not push him away anymore.”
Source: Dragonswood