The Torah allows man to focus his attention on a different dimension. Modern man has become so wrapped up in the physical concept of pleasure that he misunderstands this asssertion of the Mishna, taking it as a rejoinder to men of unceasing ambition. Chazal are saying more than 'make do with what you have'. They are teaching that true happiness is self-contained. The chase for external means of gratification is therefore doomed to failure, for it will never provide a healthy sense of self.
Happiness lies within.
The petty vanities that man collects in pursuit of fame and honor will never substitute for a life of content fulfillment. But to sense the truth, the soul of man must be untainted. Once he has assimilated the values of his surroundings, he is no longer free to clearly see the word of G-d, to study His law. This is the way of Torah - bread with salt, water in measure. Not that the Torah demands asceticsm, or a life devoid of pleasure.