I was reading Adam Smith today for some improbable and incomprehensible reason when I came across this great quote on happiness from the founder (more accurately, the first intellectual defender) of free-trade and Capitalism:
The great source of both the misery and disorders of human life, seems to arise from over-rating the difference between one permanent situation and another… In all the ordinary situations of human life, a well-disposed mind may be equally calm, equally cheerful, and equally contented. Some of those situations may, no doubt, deserve to be preferred to others: but none of them can deserve to be pursued with that passionate ardour which drives us to violate the rules either of prudence or of justice; or to corrupt the future tranquillity of our minds, either by shame from the remembrance of our own folly, or by remorse from the horror of our own injustice.
– Adam Smith, 1759
In other words, unbounded ambitions and unbounded fears lead to unclear goals, gross excesses, and no satisfaction.