A mental illness that affects the ego, causes hallucinations, and most people with the illness have the never ending need to win. They believe other people have mental illnesses, but really it is them that suffers. Most often found in athletes (football players). So named after the first person thought to have the disease, a young man named Jamarr who thought he could beat a certain girl, but it turns out she found out about his disease, and found him help.
Dude, I think you have jamarrsego.