Opportunity (n.) knocks at every man's door once in a life, but in a good many cases the man is in a neighboring saloon and does not hear her.
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Definition.com
Opportunity (n.) some people can only see after it has ceased to be one.
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Opportunity (n.) is all that life has to offer. There is no security in life, only opportunity.
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Opportunity (n.) always looks bigger going than coming.
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The Opportunity (n.) is, when lost, a pathos only the old can fully know: anybody who has reached the turn of life finds his history mile-stoned all the way with the lost opportunity.