“For if we allow that human life is always guided by reason, we destroy the premise that life is possible at all.”

Source: Globalization: The Human Consequences

Source: Happier: Learn the Secrets to Daily Joy and Lasting Fulfillment

Variant (perhaps a paraphrase of this passage): It is not reason which is the guide of life, but custom.
An Enquiry Concerning Human Understanding (1748)
Context: Custom, then, is the great guide of human life. It is that principle alone which renders our experience useful to us, and makes us expect, for the future, a similar train of events with those which have appeared in the past. Without the influence of custom, we should be entirely ignorant of every matter of fact beyond what is immediately present to the memory and senses. We should never know how to adjust means to ends, or to employ our natural powers in the production of any effect. There would be an end at once of all action, as well as of the chief part of speculation.

Speaking regarding his veto of the most recent stem cell research bill http://georgewbush-whitehouse.archives.gov/news/releases/2007/06/20070620-8.html (June 20, 2007)
2000s, 2007

Quote reported in Josiah Hotchkiss Gilbert, Dictionary of Burning Words of Brilliant Writers (1895). p. 366.
Dictionary of Burning Words of Brilliant Writers (1895)

Source: Terrorism and Communism (1920), Chapter three, p. 53

Original: (it) Nella vita, per un motivo o per un altro, siamo tutti schiavi del potere.
Source: prevale.net