But positive thinking is not only a water carrier for the business world, excusing its excesses and masking its follies. The promotion of positive thinking has become a minor industry in its own right, producing an endless flow of books, DVDs and other products; providing employment for tens of thousands of "life coaches" "executive coaches," and motivational speakers as well as for the growing cadre of professional psychologists who seek to train them.
A "water carrier" is a drudge, a drone, someone who is not the leader or the star of the effort, someone who has been relegated to a support position. In American football, it is the waterboy. In bicycle racing, the use of "water carrier" was solidified in the film about the 1973 Giro d'Italia: "The Stars and Water Carriers".
A water carrier is not, typically, deemed capable of winning the objective. They might possess talent, but it is considered a lesser talent. There are occasions where someone who is otherwise a star acts as a water carrier for a team mate who has a better chance of winning, given the circumstances. This is an act of humility, to demonstrate one's ability to forego personal goals for those of the team.
I guess the author used the term as defined at #6 in Your Dictionary:
- (figuratively, colloquial) An individual doing simple, ordinary work, usually in opposition to somebody considered more valuable.
So the positive thinking does not only do the ordinary work in the business world, excusing its excesses and masking its follies, but also aces it.