Agreed. I do think that in some cases (most humans) we could do with a fair bit less of the lingering pain, and that is why I use painkillers when injured and treat my symptoms when ill (generally speaking).

In reference to the original discussion, unhappiness and anger tend to be more like lingering pain than the instant pain of injury. And while these negative emotions are useful, we often do not need the full "dosage" that our brain supplies (of course, the dosage varies widely from person to person)