What do Vincent Van Gogh, Edgar Allen Poe, Winston Churchill, Abraham Lincoln, Mozart, Michelangelo, Hans Christian Anderson, Agatha Christie, Charles Dickens, Paul Gauguin, Emily Dickinson, Leo Tolstoy and Ernest Hemingway all have in common?

These are people who literally changed the world, who blasted the status quo apart with works of art or music or writing or political acumen. Their contributions stand today as some of the most progressive, startling, and beautiful on earth, and the list above is far from complete.

But there’s something else that unites them, can you guess?

They were all severely depressed through most of their lives.

Some of the greatest artists, writers, musicians and leaders became great not in spite of but because of their ability to plumb the darkest depths of the human soul and emerge with fists full of fodder for their art.

Are you sanguine, happy-go-lucky, and generally cheerful? You may think depressed people are real bummers, but let me tell you something: you need us. The world needs the melancholic, the depressive, the dark thinker. And why? We keep you honest. We keep you grounded. When you want to skip through the daisies and click your heels together, we remind you that life is finite, that mortality is certain, and that death is a guarantee. We open your eyes to the knowledge that you are merely a vapor’s breath upon this earth, and thus you are urged to act accordingly.

The sanguine who has no melancholy friend to balance them lacks substance and runs the risk of being indifferent to human suffering. One study showed that happy people tend to be less able to empathize with others than sad people are. I maintain that this is because perpetually happy people live in a protective bubble of happiness; a bubble that sad people do not have, and a bubble that tends to keep one from seeing clearly.

Most happy people seem to believe that hanging on to a depressed friend is an act of generosity towards that person, but the truth is, that sad friend has much to offer. Their gloom may make you uncomfortable, but discomfort is often what is needed for growth to occur.

Stick around the depressive for long enough, and you may find yourself gaining valuable perspective that you did not have before. You may find, in the end, that you need your depressed friend even more than they need you.