Take away their freedom. When people lack the freedom to speak, work, and conduct their lives according to their wills, they are forced to self-regulate. Self-regulation causes awareness of the self. The more aware of themselves they are, the more depressed they get.
People are happy when they aren't aware of their own feelings, which is a form of blissful unawareness, the state of the Dao. They struggle when they get self-conscious. They suddenly now have to deal with their memories which bring back the illusions of time, past, etc. The more they focus on themselves, the more they ruminate about opportunities lost, past mess-ups and what they could have done. It is natural to make mistakes but the self-aware man's incessant pondering makes him hate himself for his errors. The religious beat themselves up even more. They call these errors sins when none of it really exists anymore.
The past exists only in the minds of men. The human mind links the episodes of its memory together into a continuous experience it perceives as time. The summary of the memories becomes self-perception. In the vision of the past, if people see themselves doing what they define as bad things, they consider themselves bad. All attributes that people allow themselves, extroverts, introverts, good, evil, etc are nothing but summaries of the past, which does not exist beyond the confines of the ego.
When people are free from the fear of the law, traditions, and customs, they allow themselves to pursue their wills or they let their wills happen. When they allow things to unfold, they become unaware of doing anything with the intent of doing it. They become non-doer doers. Everything flows by itself. The weight is lifted. They no longer have to self-regulate. The self, thus, dissolves, just like the illusion it always was. Suddenly, they are free, of themselves.