The tendency to encourage youngsters to believe they can be whatever they want to be is a by-product of the cult of positive thinking, which has been tackled head-on by journalist Oliver Burkeman in his book The Antidote: Happiness for people who can't stand positive thinking.
Burkeman begins by reporting on a Get Motivated! seminar in San Antonio, Texas. An 83-year-old self-help guru has a message that will change the 15,000-strong audience's lives forever: "Cut the word 'impossible' out of your life."
He says "impossible" has proven to be "a very stupid word" because when he was a child people didn't think it was possible a man could walk on the Moon or have his faulty heart replaced by one removed from someone who had no further use for it.
Thus positive thinking is revealed as 21st century snake oil: the secret to success and happiness in one convenient package. Don't listen to what history and common sense are telling you - that it can't possibly be that easy. Swallow what I'm selling and all your troubles will be over.
The fact that some people living in the 1930s assumed the future would look pretty much like the present because they lacked the background and imagination to sense the transformative power of technology doesn't invalidate the word "impossible" at all. No doubt some of their contemporaries thought otherwise; 500 years ago Leonardo da Vinci anticipated the helicopter.
To those who want to purge the dictionary of "impossible", I offer this challenge: clear the Southern Alps in a single, unassisted leap. By all means take a run-up if you think it would help.
There's nothing wrong with goal-setting and positive visualisation. The problem is the claims made on their behalf. If you don't have a clear idea of where you want to go, it's less likely that you'll get to what would have been your desired destination had you gone to the trouble of sitting down and thinking it through.
On the other hand, if achieving great things was just a matter of making a list, every second person would be setting the world on fire.
Furthermore, in a competitive world, success is often at someone else's expense: for every winner, there has to be at least one loser. We often hear winning teams talk about the goals they had set themselves; for obvious reasons no one bothers to ask losers what their goals were.
American imperialism is what happens when the sole superpower is the spiritual home of positive thinking. America has the means to intervene anywhere in the world, and the optimism to believe it can solve any problem. The War on Drugs is a textbook example of what can happen when a rich, powerful and optimistic nation sets out to solve a problem that those with some understanding of human nature, some awareness of history and the law of supply and demand and a degree of rational pessimism know is insoluble.
But because failure is not an option - another of the positive thinking brigade's terrifyingly unworldly mantras - the response has been to swing the sledgehammer even harder, rather than rethink the strategy from the core assumptions up.
There used to be a military axiom that you should never squander resources on a lost cause. No doubt it has been expunged from the manuals by the positivity police who disregard human fallibility despite being surrounded by evidence of its influence on our affairs.
