Yes, I think that makes a lot of sense. Even adults get upset or angry over little things when really there is some bigger underlying issue bothering them.
I'd say just to recognize his feelings of sadness and comfort him. Validate that his sad feelings are ok to have. Hold him if he likes to be held. Maybe try not to reason with him about his unreasonable requests, but commiserate with him about feeling sad about wanting something he can't have.
I think I read in the book Emotional Intelligence that being able to recognize your own feelings and where they're coming from is a key to being emotionally stable as an adult and also being able to relate to others emotionally. Some people never become very emotionally self-aware, but for most children it just takes time as they grow older.