The second story in Chapter Four of the Zhuangzi begins with a lengthy whine by an ambassador about his anxieties concerning his latest mission, followed by a long-winded response by 'Confucius', none of which seems typically Zhuangzian. The concluding paragraph, however, is vintage Zhuangzi:
"Just ride along with things [events] as you let your mind wander. Entrust yourself to inevitability and thereby nourish what is central. . . . Nothing is better than to fulfill your destiny, but that's the hardest of all." (Mair)
These two imperatives essentially exhort to the same thing and are at the heart of Daoist spirituality: fulfill your destiny. We are able to "ride along with events" because our mind wanders free of them. This is not resignation, but empowerment. It refers us back to the description of the one who "relies on nothing" and is thereby able to "chariot on what is true of both heaven and of earth". Yet paradoxically, this empowerment requires that we "entrust" ourselves to that over which we have no power.
But what does it mean to fulfill one's destiny (ming)? We must first understand that destiny (fate) has absolutely nothing to do with something preordained; nothing could be farther removed from the Daoist sense of the spontaneous emergence (ziran) of apparent reality. Henry Skaja ("How to Interpret Chapter 16 of the Zhuangzi"; Wandering at Ease in the Zhuangzi) writes, "Although ming may be impossible to change, this does not imply that ming means 'fate' or 'destiny' in the deterministic sense of predetermination by a presupposed causal agent." He goes on to quote Mencius: "Though no one acts and yet there is activity — this is tian [heaven]. Although no one directs something to happen and yet it does happen — this is ming." (5A6)
Philosophical Daoism (by which Mencius was much influenced despite his Confucian credentials) would fully agree with this understanding of ming only it would add, I think, that what is done by someone else is also my fate to the extent that it affects me. In other words, it may not be fate for someone to steal from me, but it is my fate to have been stolen from. Whatever happens to me is my fate, and ultimately, no distinction need be made between what could not have been otherwise (being born crippled, for instance) and what could have been otherwise had someone behaved differently.
To fulfill one's destiny, therefore, is not to become or achieve something preordained, but simply to thankfully embrace everything that comes one's way. If this is doing, it is all that need be done. And yet, as Zhuangzi says, it is the "hardest thing of all".
A parallel analogy might shed some light on this idea of “fulfilling”. Guo Xiang, commenting on the relative size of each thing’s fated givens, whether the vastness of Peng or the tininess of a quail, tells us that, “Since each fits perfectly into precisely the position it occupies, all are equally far-reaching and unfettered.” (Ziporyn) “Fulfilling one’s destiny” is fully occupying the totality of one’s experience. This is true empowerment.
You can check out Scott's writings on Zhuangzi here.