Last year my friend Ben blogged about which traits increase in value "nonstop," meaning that more of the trait is always better. He correctly pointed out that few traits fit this criteria. For example, it is good to have more flexibility up to a point, but too much and you'll never get anything done. To him, persistence was one the few traits without this backstop.
I think that empathy is another one. Sure, you can be too kind (telling someone "you're welcome" all the time gets annoying), but you can't be too empathic. Indeed, boosting your empathy is undoubtedly a positive personality change, since it will put you more at peace with your own place in the world.
Of course this is largely semantics but it's still a stimulating thought exercise. Can you think of any other such traits?
(Thanks to Joey D for sparking a conversation about this idea.)