My senior year in college, a close friend was hospitalized after a nervous breakdown. A few years later, I ran into her on Fifth Avenue in New York City.

We became friends again, and one day over coffee she confided to me that during her breakdown, she was convinced all of her friends were trying to kill her.

It was strange, she said, being my friend again, since there was a part of her that still believed I wanted to kill her, even though she knew this wasn’t true.

“I can’t ever really trust my thoughts anymore,” she said. I felt sorry for her — how terrible it must be, I thought, to not trust your thoughts.

Now, more than 40 years later, I no longer feel sorry for her. She was halfway on to a basic truth: Nobody’s thinking can be trusted.

What thinking does is create a facsimile of the world. If our facsimile is too far off from the facsimiles around us, we are deemed to be crazy. If it pretty much agrees with most other facsimiles around us, we are deemed sane. But the facsimile is never exact, and if we trust our thinking so much that we forget it is only an imitation of the real thing, we get ourselves and everyone else into trouble.

My friend had at least a partial glimpse of this in her mid-20s. The rest of us should be so lucky.

It’s not as if the unreliability of our thinking is news. It’s the basic plot hinge in both comedy and tragedy. Manipulating our thinking is the basic technique of professional magicians. And as for the perceptions on which our thinking is based, every cop, lawyer and judge knows that eyewitnesses are unreliable.

Everybody knows this, but no one wants to apply it to themselves. “Sure, people easily delude themselves, but not me!” Sorry to mention this, but: yes, you.

Is this depressing news? Actually, it’s exhilarating. At some level, we all recognize that our thinking is a kind of prison. Tremendous energy goes into creating distractions, from Angry Birds to Wild Turkey, to help us forget we’re in this prison. But distraction, while entertaining, doesn’t get us out of this particular jail.

Instead of being distracted, we need to really pay attention. Each of us is her own jailer; there’s nobody else to blame.

That means that each of us can become free. In fact each of us is, already, intrinsically free. The walls of our prison are as insubstantial as ghosts. It’s like looking through a window: You can see the window, or you can see what’s on the other side.

“Whoever you are: in the evening, step out of your room where you know everything,” wrote Rainer Maria Rilke. Why live in the cramped world we create in our heads? Step out in the evening, in the morning, at night and at noon, into the world as it really is. What have you got to lose?