The #3 2018 Watchtower made the point about healing: "Consider: If the Creator designed our bodies to heal physical wounds, can we not have confidence in his promise to help us recover from emotional injuries, too?"
Two things interfere, qualifying the healing to a "help us" healing. 1. The mind is in the business of remembering, unlike the knee you scrape, 2. With the knee you scrape, you can get it away from whatever scraped it. In this system, that can be more of a challenge, and won't completely cure out until the new system. As one brother said somewhere on the broadcast: 'In the new system, resurrected people will look back and say 'how could you ever have lived during those times, with the constant stress?"