The old waiter refers to his inability to sleep at the end of the story as “insomnia.” Explain and justify.

Insomnia is something the old waiter attributes to many; "After all, he said to himself, it's probably only insomnia. Many must have it." In context, we can infer that for many..... life at the cafe is all the "light" they have in their life, and that insomnia, is a fear of the end of their life. An unsettled life, lived for the most part, alone.