'Labors' in the Bible

What does man gain from all his labor in which he labors under the sun?

For what has a man of all his labor, and of the striving of his heart, in which he labors under the sun?

What profit has he who works in that in which he labors?

This also is a grievous evil, that in all points as he came, so shall he go. And what profit does he have who labors for the wind?

Behold, that which I have seen to be good and proper is for one to eat and to drink, and to enjoy good in all his labor, in which he labors under the sun, all the days of his life which God has given him; for this is his portion.

then I saw all the work of God, that man can't find out the work that is done under the sun, because however much a man labors to seek it out, yet he won't find it. Yes even though a wise man thinks he can comprehend it, he won't be able to find it.