'Hard' in the Bible

And I gave my heart to searching out in wisdom all things which are done under heaven: it is a hard thing which God has put on the sons of men to do.

Then I examined all of my accomplishments that I had brought about by my own efforts, including the work that I had labored so hard to complete and it was all pointless, like chasing after the wind, and there was nothing to be gained on earth.

So I loathed all the fruit of my effort, for which I worked so hard on earth, because I must leave it behind in the hands of my successor.

So I began to despair about all the fruit of my labor for which I worked so hard on earth.

I have seen personally what is the only beneficial and appropriate course of action for people: to eat and drink, and find enjoyment in all their hard work on earth during the few days of their life which God has given them, for this is their reward.

There is an evil which I have seen under the sun, and it is hard on men;

Who is like the wise man? and to whom is the sense of anything clear? A man's wisdom makes his face shining, and his hard face will be changed.

I observed all the work of God and concluded that man is unable to discover the work that is done under the sun. Even though a man labors hard to explore it, he cannot find it; even if the wise man claims to know it, he is unable to discover it.

The fool is so worn out by a hard day's work {he cannot even find his way home at night}.