Invisible disease. I have one. Since 1975 (and probably before) I have had Lupus. I have the more deadly firm called Systemic Lupus Erythematosus. It is an autoimmune disorder. My immune system has at times attacked my kidneys, my spleen and other organs. It has placed my body under such stress that all vital systems shut down. I died once and was brought back using a defibulator.
I take quite a drug cocktail to keep going. I have been taking steroids since 1975.
At one time there were few options for people with Lupus. I was told in 1976 that I might not live to see the age of 45. I'm now 69 years old. Through drug therapy I have been able to avoid life threatening flare ups. Only one flare up occured a few years after diagnosis when Lupus put me in a coma for over a week as it cause inflammation of the tissue lining the arterial walls cutting blood supply to the brain.
This has been my life so far. I was once on permanent disability but opted out of that program and got a degree and had a good career.
So don't be so quick to judge when you see a person. They might be suffering from an invisible disability or some orphan disease.