I like Dale Carnegie in general and think his intentions are good, but disagree with this quote. A different user posted this link a couple weeks ago, I find it relevant: http://scholarworks.umass.edu/cgi/viewcontent.cgi?article=1004&context=eng_faculty_pubs
Naive believing is easy, but not sophisticated believing. This is similar to how naive doubt regularly fails.
Quotes are a unique enough medium of expression that I'm interested in viewing quotes that people have found collectable, emotionally impactful, useful, memorable, or otherwise noteworthy - perhaps others are similarly interested. To clarify, these need not be even remotely related to rationality. I'm hijacking the mandates traditionally used for the Rationality Quotes thread, with a few modifications:
Please post any meta discussion in the top-level comment named "Meta".