The greater the antagonism there is to the pain-relieving drug, then the larger the dose should be. But because pain is antagonistic to opioids, there should be no respiratory distress and no euphoria. Patients will take them until the pain is controlled, or gone. Then patients are happy to discontinue the drug. At this point, the patient can't function as an intact human being, and we need to turn our efforts towards restoring that person to who she or he was before.
Pain produces anxiety and depression and fear.
It makes people angry. Good pain management is multi-disciplinary because pain is complex.