"Overly rosy promises are regularly offered by politicians, manufacturers, car salespeople, real estate agents, and nearly anyone trying to influence anyone else. Promises are the stuff of courtship or reassurance, particularly when people would rather deny the downside... This human tendency is exacerbated by systemic complexity. Economists know that forecasting is a dangerous occupation, especially about the future — which is funny but not a joke. In complex systems, inherent uncertainty joins with volatility to increase the likelihood that forecasts fall short."
"But lest we turn into a nation of cynics, promises should be kept realistic from the start. Leaders should be courageous about revealing that they don't control everything and don't know exactly how the future will unfold. The one promise they can reliably keep is to communicate often, with alternative scenarios in mind. In general, under-promising and over-delivering produces much more delight than over-promising and under-delivering. We are so braced for disappointment that a happy surprise stands out."