The professional world abounds in Narcissists, those with an unusually high sense of their own awesomeness. Whether you are a Narcissist, or have to deal with one, it helps to have a nuanced understanding of this syndrome.
The first type. Is skilled. Accomplished. Perhaps decorated by the world. Has mapped the perimeters of his domain and sees himself as unassailable. The second type. Is willing to be skilled. Yet to accomplish anything significant. Decorates himself. Has no inkling of his boundaries, or what lurks beyond its little borders.
The first can, with a dose of humility, return to his brilliant beginnings. Perhaps even expand the borders of his influence and have men follow his banner. The second lives too deep in his own imaginings. Quirks of fate could yet wake him.
Having been both these types at various stages of my life, and recovered by fortuitous circumstances that were not all benign, a few words that might help. If only to recover from this malaise or perhaps to put up with one afflicted. Be understanding and tolerant of the first, make them see what lies beyond and things might change. The second might need methods that are either too subtle or cruder than what you are capable of, leave it to the vagaries of time to set things right.
For yourself, choose action that grows the good virtues within. Let these be a reminder of how pride in any accomplishment, when not tempered by humility, can lead you astray. Remember your falls as you march forward.