'Painful' in the Bible

I have seen the task which God has given to the sons of men with which to occupy themselves.

I have seen that every [effort in] labor and every skill in work comes from man’s rivalry with his neighbor. This too is vanity (futility, false pride) and chasing after the wind.

One hand full of rest and patience is better than two fists full of labor and chasing after the wind.

There was a certain man—without a dependent, having neither a child nor a brother, yet there was no end to all his labor. Indeed, his eyes were not satisfied with riches and he never asked, “For whom do I labor and deprive myself of pleasure?” This too is vanity (a wisp of smoke, self-conceit); yes, it is a painful effort and an unhappy task.

For the dream comes through much effort, and the voice of the fool through many words.

When I applied my mind to know wisdom and to see the activities [of mankind] that take place upon the earth—how some men seem to sleep neither day nor night—