Individuals with grandiose delusional disorder have an over-inflated sense of self-worth. Their delusions center on their own importance, such as believing that they have done or created something of extreme value or have a "special mission."
"I think mental illness or madness can be an escape also. People don't develop a mental illness because they are in the happiest of situations usually. One doctor observed that it was rare when people were rich to become schizophrenic. If they were poor or didn't have too much money, then it was more likely. And this is natural, if things are very good, you can find satisfaction with the world as it is, as it seems to be. If things are not so good, you may be one to imagine something better.
For me, I was able to imagine myself as in a role of greater importance than I would seem to be ordinarily. At the time, I had some recognition. I was making some progress professionally, but I wasn't really at the top. I didn't have top level recognition, and so when I started thinking irrationally, I imagined myself as really on a Number 1 level. I was the most important person of the world, and people like the Pope would be just like enemies, who would try to put me down in some way or another, or the president."- Dr John Nash