Solomon introduces us to human depravity. These words relate to the final thought of the previous verse, that all is vanity and vexation of spirit.
Men and women try desperately to persuade themselves that they can make straight what is crooked, both in themselves and in the world, without the help of God. But there will always be wars, sicknesses and tragedies in the world. Human nature does not get any better from one generation to the next. Man simply substitutes easier commandments which he thinks he is capable of keeping in place of the commandments of God. Crooked in the human being cannot be made straight without God’s intervention in the life. Bad temper cannot be improved. What is the trouble? We are cut off from God. We are incomplete. We are so made that we can only function when in touch with God.