I think we all experience moments of wondering why we have to deal with a particular health challenge — what is the purpose of it? We might see ourselves as "abnormal" and wish to just be more "normal." We might look with envy on others who seem to have it "so easy" and wish that we could have some of that ease. When I did my dissertation research, "Why me?" was a commonly reported thought among women with chronic pelvic pain. Some even wondered why God had given them such debilitating pain and illness.
Sometimes we just reach a threshold of not wanting to deal with chronic illness or chronic pain anymore. All of our excellent coping strategies fall by the wayside because we're just too tired to apply them. We feel mentally defeated in those moments. And we can't seem to just talk ourselves out of them. The sense of defeat and demoralization is too strong.
When we are absorbed in the "why me?" of coping with a health challenge, it just seems awful. Suffering isn't rational! The "why me" comes from the feeling of being sucked into a "me bubble" of despair.