מוסר אויף קהלת 1:2

In the first chapter we shall speak about the quality of pride. How good it is that it occurs at the very beginning of all the chapters because of the obligation of man to separate himself from it! For pride is the doorway to many evils and we have seen nothing as evil as arrogance in all of the qualities. Therefore, a man must be wise and lead pride along paths that are worthy, and thrust it away from the place where it is not proper for it to be.

And in truth, what there is to be happy about regarding the good of this world and on being rescued from evils is that through life and the good [of this world], we have the ability to come to the great good, which is to serve our Creator. And this is the evil of misfortune and death — that they prevent us from serving our Creator, for in any case [the tragedy incurred] is the same. For our days are as a passing shadow, and the evils and the good of this world are fleeting; “Breath of breaths, everything is a breath.” (Ecclesiastes 1:2). Yet we desire with life and goodness because it appears to us that it assists us in the service of the Holy One, blessed be His name. And this is the intention of what we say in “nishmat kol chai” after “and if our mouths were filled with song as the sea etc.”: “Until now, your mercies have helped us”. We wish to say, “You have gladdened us with all the goodness and saved us from evils in order to mercifully assist us in your service”.

And King Solomon, peace be upon him, essentially composed the book of Ecclesiastes in order that man put to his heart that the world is a vanity of vanities and [that] he only use it for the service of the Creator, may He be elevated. And he made his intention known in his introduction and his conclusion: For he opened and said, (Ecclesiastes 1:2), "Vanity of vanities, said Kohelet, vanity of vanities - everything is vanity." And our Rabbis, may their memory be blessed, said (Kohelet Rabbah 3:13), "If another man had said this, we would have said, 'Maybe he has not gathered two small coins in his entire days; therefore the world is considered like vanity in his eyes.' However it is appropriate for King Solomon - about whom it is written (I Kings 1:27), 'The king made silver as plentiful in Jerusalem as stones' -to say that the world is vanity of vanities." And he concluded his book and said (Ecclesiastes 12:13), "The sum of the matter, when all is said and done; revere God and observe His commandments, for this is all of man."