What I find weird is that it seems like the body can be in permanent pain, but it isn't able to achieve a permanent state of feeling good.
For instance, there are people with spine damage who feel chronic, unrelenting pain every day of their life. On the other hand, for any drug that makes you "feel good" (oxycodone, morphine, even Adderall), your body eventually builds a tolerance and requires more and more of that substance to achieve the same level of "happy". So why doesn't the body do that with pain — where it eventually gets used to your "average pain state" and requires ever more intense infliction to feel the same level of "hurt"?
At the risk of an evolutionary just so story I think "feeling good" is a larger risk for our animal ancestors.
Not standing in fire is always relevant even if your leg is broken. However, not finding a mate because you just ate, or not eating because you found a mate is counter productive.
Also, as I understand it evolution cares less about edge cases than we do. Improving average outcomes can be worth not regrowing limbs for example.
For instance, there are people with spine damage who feel chronic, unrelenting pain every day of their life. On the other hand, for any drug that makes you "feel good" (oxycodone, morphine, even Adderall), your body eventually builds a tolerance and requires more and more of that substance to achieve the same level of "happy". So why doesn't the body do that with pain — where it eventually gets used to your "average pain state" and requires ever more intense infliction to feel the same level of "hurt"?