Robertson Davies said this quote

Pessimism is a very easy way out when you’re considering what life really is, because pessimism is a short view of life. If you look at what is happening around us today and what has happened just since you were born, you can’t help but feel that life is a terrible complexity of problems and illnesses of one sort or another. But if you look back a few thousand years, you realize that we have advanced fantastically from the day when the first amoeba crawled out of the slime and made its adventure on land. If you take a long view, I do not see how you can be pessimistic about the future of man or the future of the world.