The eagle does not catch flies.
This is a proverb from the time of the Roman Empire and has passed into many languages. The eagle standard that led the all-conquering army symbolized the mighty ambitions of the rulers of Rome.
Obviously a large bird of prey has to hunt animals of a reasonable size to justify the time and effort and it is this underlying principle that gives the proverb meaning.
One relevant aspect of this saying for today is a caution not to spend time and energy pursuing the insignificant. Everyone is very busy but do we always do too many niggling little tasks when we would be better focussing on major ones? Getting your priorities right means dealing with the big issues and not being bogged down in matters that can wait or be avoided. You might be convincing yourself that you are busy but unless the time and effort produces a meaningful return you are simple wasting time.