The tersest phrasing I've seen was "You get more of what you reward, less of what you punish". Google finds a 1990 book calling it an "old adage" so I've no idea what the source is.
From what I've read there is one important exception, though: if you apply an extrinsic reward or punishment to a behavior, people can see this as a replacement for rather than a supplement to whatever intrinsic rewards or punishments they had previously associated with that behavior, and this can actually reduce the desired behavior.
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".