"Ecclesiastes" is one of 24 books of the Tanakh or Hebrew Bible, where it is classified as one of the Ketuvim (or "Writings"). It is among the canonical Sapiential_books/Wisdom Books in the Old Testament of most Christian_denominations/denominations of Christianity. The title Ecclesiastes is a Latin transliteration of the Greek translation of the Hebrew "Koheleth" (meaning "Gatherer", but traditionally translated as "Teacher" or "Preacher"), the eponymous author of the book.

More Ecclesiastes on Wikipedia.

Give not over thy soul to sorrow; and afflict not thyself in thy own counsel. Gladness of heart is the life of man and the joyfulness of man is length of days.

Be not slow to visit the sick.

Let your heart give you joy in all the days of your life.

I have also learned why people work so hard to succeed: It is because they envy the things their neighbors have. But it is useless. It is like chasing the wind...It is better to have only a little, with peace of mind, than be busy all the time with both hands, trying to catch the wind.

It gives you life, but you can't hold on to it. You can't breathe indefinitely. We need to surrender to the fact that all efforts at permanence are hopeless. No structure we can build will protect us from the contingencies of life. But in the midst of that impermanence is the incredible gift of life.

That which is crooked cannot be made straight and that which is wanting cannot be numbered.

A threefold cord is not quickly broken.