The pain that surfaced as Walker literally played with his own life was something that he could not understand. But something that he also felt was completely right to happen.
healing the body or changing the body with training always came with some pain, the healing pain was because the body was changing and growing to repair itself. The changes caused the body to stretch and change in ways that it didn't before.
The wounds would always be sore, the very same way that the body was sore after training physically for a long or hard time. Therefore, the life mana would naturally react to those things.
Walker had already understood how the body and life mana would work together. The life mana could spur the body to heal better because that was how the body worked. Using light magic or other healing skills would focus on the body purely. That allowed it to heal and regenerate using the nearby nutrients stored within the body.
