I've long wondered about that. The answer seems to be that Nixon truly was paranoid and never felt like his position was safe, even when it was.
Okay all you people out there wondering about Watergate, Nixon had nothing to do with it.
Read the book "Silent Coup: The Removal of a President" and you will learn more about Watergate and what really went on, clue, John Dean was a lot more involved than has ever been reported for motives of his own.