The pain that lasted with Morrie for over a period of 20 years was the fact that he had the Amyotrophic lateral sclerosis (ALS),
This is a disease that is known to affect a person's neurological system. The Lou Gehrig's disease is another form odf this.
It is degenerative in nature and would affect a persons muscles. Morrie suffers from the pain throughout the novel.
Read more on Amyotrophic lateral sclerosis (ALS) here https://brainly.com/question/24962902
