Never do anything on principle alone. If the principle of the thing is the only reason to do it, don't.
-- Bill Bryson
I think this is a bad principle to try to uphold. It means you have to understand the motivations behind all your principles, rather than just knowing that they are good principles. Which may be valuable for a small class of philosophers, but it's wasted effort for the general population.
Here's the new thread for posting quotes, with the usual rules: