What is the difference between a disorder and the normal range of abilities and personality?

Great question! We all have tendencies that if more extreme would qualify us as having some psychiatric diagnoses. A tendency or problem behavior becomes a "disorder" when it significantly and repeatedly: (1) affects us adversely; (2) limits our capacity to succeed; (3) disrupts our relationships; and/or (4) limits our personal happiness and self-esteem.
Time and functioning. Psychological symptoms, behavioral traits, or intelligence abilities are generally considered a disorder if they continue for a long time and cause a significant impairment to the individual's ability to function normally in his society.