Authenticity
Inauthenticity is easy; we only have to think.
As Nietzsche points out, the most inauthentic part of us is our intellect. It can and does invent any old story in an attempt to make things okay. This is the intellect's primary function: to solve problems. Unfortunately, life has no regard for whether things are okay for us. Life can be difficult in many ways, including financially, health-wise, and in relationships, and we don't particularly like the idea that one day we will no longer exist. The potential for misery and despair is considerable, and we don't need a traumatic event in our lives for us to feel that life is barely worth the effort.