Secure your fate with honor; do not rely on chance or (worse) duplicity to do so. What do I mean by this? He who wins the lottery has not, as a result, learned to win future lotteries any better. Accept unexpected gifts heartily; however, do not depend on them. A good day, self-earned, is the seed of perennial blessings.
In the same way, an army that wins a battle through trickery has won the day and the day only. A foe defeated through deceit tends not to be convinced of their comparative weakness and, thus, is more likely to rally and fight again. Battles fought with honor and won win weeks, wars, and sometimes even eras.