Heaven and earth last for ever.
Why do heaven and earth last for ever?
They are unborn,
So ever living.
The sage stays behind, thus he is ahead.
He is detached, thus he is one with all.
Through selfless action he attains fulfilment.
 The Ma wang tui text and several others read this as being because they do not live for themselves.
 Most texts read this as a rhetorical question alon the lines of 'Is it not because of selfless action that he attains fulfilment?'
Of course, the idea of being unborn and therefore ever-living is is an important one, and a fair description of the nature of mind and of emptiness, but these ideas are more Buddhist than they are Taoist, especialy early Taoist.
Wang Pi says: If one exists for oneself one will contend with others, whereas others come and submit themselves to those who do not exist for themselves... To be utterly free of self-interest means to make no conscious effort for one's own sake. Such persons will always find themselves pushed to the fore and their selves preserved will-nilly...
Cheng says that - basing himself in non-action - the sage considers himself an 'outsider' and left behind., whereas those who act consciously will always only fail.