Perfection is defined by Wikipedia as "a state of completeness and flawlessness".
For whatever reason, it seems that humans can't reach that state in every aspect of their lives, i.e. even if everything seems to be perfect in that beings life, something happens and an aspect is imperfect again.
Theoretically, if one had to make a minimum of one mistake (such as choosing a personally unmoral decision) to ensure the balance of perfect/non-perfect, or "fate" would cause an imperfection for you, wouldn't it be better to choose what you fail at/make a mistake you know is a mistake, so you can succeed at the things you really want to?