If samsara is the illness, what is its cause?
The Gita's answer is direct, and at first strange. It is not your situation, not your past, not your temperament. It is something more basic.
Consider what happens when someone asks: who are you? You answer with your name, your work, your roles, your story. You point to your body, to the mind reading these words. The answers come easily, because they are the closest things to hand. But the mind has been asked a question it has no real answer to. Rather than admit the gap, it fills it with whatever is nearest. The answer is not arrived at by looking. It is arrived at by default.
Because you take yourself to be these things, you take on their fate. The body will die one day. The mind will stop functioning. The roles change. The story keeps being rewritten. So you take yourself to be temporary too — fragile, breakable, on borrowed time.
And small. A body has limited strength, limited reach, limited control. The world around it is vast and far more powerful: illness, accidents, the economy, other people's choices, events no one sees coming. A self that small needs protection. It needs things to go its way. Left to itself, it feels exposed.
You rarely put this into words, and nothing in your experience has ever contradicted it. If anything, life keeps confirming it: people fall ill, jobs are lost, those you love die. This is the root of your anxiety. You may think you are anxious about your job, your health, or whether a relationship will last. Those are only the occasions.
It also explains the cycle the last piece described — the lift that fades, the low hum that returns. Each thing you reach for is meant to complete a self you take to be small and incomplete. No achievement can do that, because the lack was never in your circumstances. It was in your idea of what you are: I am not enough as I am. To make up the difference, I have to get something, do something, become something. And the clock is ticking.
You may not find this belief in your opinions. You will find it in your reactions. The next time something goes wrong — a project fails, someone criticizes you — notice the small drop in the stomach, the flash of panic. That is the belief talking.
So the real work, the Gita says, is not to manage samsara better. It is to see through the mistake that gives it its power.
So what are you, if not these things?
What you actually are is not the body, not the mind, not the roles, not the story. These can be known by the senses. They can be looked at, examined, measured. You yourself cannot be known that way, because you are the one looking through the senses. You cannot turn the eye upon itself. You cannot make the seer into a thing seen.
This sounds, at first, like a dead end. If you cannot know yourself the way you know objects, then how can you know yourself at all?