Delusions

Delusions and all it mights. What is actually the definition of delusions? Isn’t by labeling delusions easily to some stories regarded ridiculous, we are actually limiting our own mindset? What if we are the one who’s limiting ourself toward a further understanding of how the mindset works? Basicly I believe that all mindset are in some way twisted with their own typicalities.
Delusions are oftenly refered to manic bipolars and its symptoms. It also could work otherwise, as depression toward something. For instance, someone feel depressed because he believed that he was the one responsible for the death of many British people during the Gulf War (read Measuring Psychopathology by Anne Farmer). But somehow there lies the typicalities: pride of holding certain gift, talents, abilties, name it. Basicly it was only two distinguished branches that emerges from the very same root.
So isn’t the idea is somewhat categorizing by categorizing itself? Thus the limit of mindset is shrinked. Or perhaps I just need to do further reading before I reach any single premis or inference.