Aleksander Solzhenitsyn

He had drawn many a thousand of these rations in prisons and camps, and though he'd never had an opportunity to weight them on scales, and although, being a man of timid nature, he knew no way of standing up for his rights, he, like every other prisoner, had discovered long ago that honest weight was never to be found in the bread-cutting. There was short weight in every ration. The only point was how short. So every day you took a look to soothe your soul - today, maybe, they haven't snitched any.

It was only when I lay there on the rotting prison straw that I sensed within myself the first stirrings of good. Gradually it was disclosed to me that the line separating good and evil passes not between states nor between social classes nor between political parties, but right through every human heart, through all human hearts. And that is why I turn back to the years of my imprisonment and say, sometimes to the astonishment of those about me, bless you, prison, for having been a part of my life.

The thoughts of a prisoner - they're not free either. They keep returning to the same things.