I have found it virtually impossible to work with a certain kind of client — the one that insists that they already know, or his colleague, the one that is afraid of looking like they don’t already know.
The result is the same — a certain lack of progress as they defend their egos against looking bad. With them, things have to start looking VERY bad before they are willing to put results over their personal view of themselves. And there are times when that approach just takes too long to make a difference.
On the opposite side of the coin, however, is the client who is willing to learn at every turn. They make the best clients, and usually become friends. The quest to do good first and foremost, helps us both to put our egos in check, and makes projects flow smoothly and sweetly, such that they hardly feel like work at all.