>"You can be president of the Unites States, if you really want to!" >This one motivates person to at least try his best >A more truthful message would be, "You have much higher odds of being struck by lightning than of ever becoming president of the United States" >This one motivates the person to sit on his backside and do nothing.

No - telling someone something so patently unlikely sets a disconnect between a goal and the effort required to reach it (as if the only thing required to be president of the USA was to want it.) Two possibilities: the person ignores the message (if they're sensible), or they take it to heart and then get dejected when they fail.

This is also the current thinking on teenage girls and anorexia; presented with supermodels in the media and the (implied) message that they should/can emulate those role models is what is thought to cause self-esteem problems in impressionable teenage girls, which can lead on to more serious disorders.

I think it would be better to teach people how to make the best of their circumstances (and by this I mean personal attributes as well as social surroundings), rather than encourage unrealistic expectations.