Any work will not get accomplished just merely by desiring for it’s completion. A ‘prey’ by itself doesn’t enter in to the sleeping lion’s mouth!!!
By giving an example of a lion the subhashitkAra here wants to emphasize that the desire and capabilities should be added by the efforts and hard work to achieve the goal! Even if the lion has the capabilities to catch it’s prey, the prey will not automatically fall in it’s mouth!!
It looks odd if teeth, hair, nails, and men are not at their proper place. Knowing this, wise man never leaves his place (occupation). This subhaShitA suggests that every body should stick to his/her duty. Doing something else is not desirable.
The sun looks alike while rising and setting. Great men too remain alike in both the good and bad times.