Pain.

Pain. If you are human, you will feel pain. It's inevitable. Physical. Emotional. Spiritual. And pain trumps just about everything. You will do or try anything to avoid or alleviate pain. You will take heavy narcotics, you will drink major quantities of alcohol, you will go to doctors, you will submit yourself to examinations, and operations, and therapies. Anything.

Witch Doctors, Faith Healers, Physical Therapists, Social Workers, Drug Dealers, Psychiatrists, Spirit Guides, Charlatans and Kooks of all types - yes, you will consult with any and all of them. Pain changes the human equation. It becomes a annoying friend who just will not take the hint to leave. It becomes a job, and a occupation.

Long-term, debilitating pain.  It's a character. It's like heavy weather. You can endure. Until you can't.