Our Personalities Are Constantly Changing, Even If We Think They’re Not

This caught my eye because a number of years ago I read a good book called "First, Break All the Rules: What the World's Greatest Managers Do Differently" which detailed the results of a survey of 80000 managers (performed by the Gallup organization), in which a main conclusion was the point that "people never change". So, when hiring people, you should expect that people will continue to behave as they have in the past.

This may seem obvious, but I've seen that a hiring manager will often hire a candidate with an unsuccessful record on the believe that, for the first time in the candidate's career, he/she will be successful in the new organization, (yes, I've done this myself also), only to be disappointed later. In fact, this pattern is really very common in my experience.