Human life the Stoics appear to have considered as a game of great skill; in which, however, there was a mixture of chance, or of what is vulgarly understood to be chance. In such games the stake is commonly a trifle, and the whole pleasure of the game arises from playing well, from playing fairly, and playing skilfully. If notwithstanding all his skill, however, the good player should, by the influence of chance, happen to lose, the loss ought to be a matter, rather of merriment, than of serious sorrow. He has made no false stroke; he has done nothing which he ought to be ashamed of; he has enjoyed completely the whole pleasure of the game. If, on the contrary, the bad player, notwithstanding all his blunders, should, in the same manner, happen to win, his success can give him but little satisfaction. He is mortified by the remembrance of all the faults which he committed. (VII.ii.28)
Thus the Stoics can be seen as having the same view of life itself that we are often encouraged to have about games: it's not whether you win or lose, but how you play. The prize for winning is far and away less important than the pride of playing well:
Human life, with all the advantages which can possibly attend it, ought, according to the Stoics, to be regarded but as a mere two-penny stake; a matter by far too insignificant to merit any anxious concern. Our only anxious concern ought to be, not about the stake, but about the proper method of playing. If we placed our happiness in winning the stake, we placed it in what depended upon causes beyond our power, and out of our direction. We necessarily exposed ourselves to perpetual fear and uneasiness, and frequently to grievous and mortifying disappointments. If we placed it in playing well, in playing fairly, in playing wisely and skilfully; in the propriety of our own conduct in short; we placed it in what, by proper discipline, education, and attention, might be altogether in our own power, and under our own direction. Our happiness was perfectly secure, and beyond the reach of fortune. (VII.ii.28)
One of the interesting things about Smith's writing is his very clever use of analogies to convey points; he must have been an excellent teacher. Here he is trying to set up the reader to understand more accurately the Stoic idea that they would probably have found most perplexing, namely, philosophical suicide. He uses a similar approach elsewhere; another very striking one is the chess-board in VI.ii.42.
One of the interesting threads in the Scottish Enlightenment is the influence of Stoicism on the major thinkers of the time. This has been studied to some extent; but it's one of those areas where more is always needed, because Scottish thinkers like Smith and Hume put an immense effort into understanding the Stoics and adapting their views to eighteenth century society.
(cross-posted at Houyhnhnm Land)