Final answer:
The narrator develops the concept of evaluating his mental and physical capacity by sharing personal feelings and reflections during the climb, which highlights the mental and physical challenges faced.
Step-by-step explanation:
The narrator in "The Final Assault" from High Adventure by Edmund Hillary develops the concept of evaluating his mental and physical capacity through the narrative by including personal feelings and reflections as he faces the challenges of climbing. Hillary describes his initial anxiety and unsteadiness, his struggle with the breakable crust of snow, and his feelings of exhaustion mixed with determination. These elements characterize the climbing experience as one that is not only physical but also mental, revealing the constant self-assessment required to ensure safety and success.