RECENTLY, I sat in a Salvation Army drop-in centre in the red-light district of Amsterdam, listening to a homeless woman speak. She was called Marie. She had a bubbly personality, and she spoke well, describing the life that alcoholism and drug dependency had brought her - not the life she had imagined for herself. She is approaching 50 now, and is free of the alcohol, although not quite clear of the drugs - well, she was clear, but only for a few weeks.

She wants not to be homeless. She has been homeless for 20 years, and now seeks a home. She is glad to have met the homeless fraternity, to have known and lived with "the hidden ones"; but does not want to stay there. As she says: "No one is born thinking: 'Oh, I hope I'm a homeless person.' But things happen."

They certainly did to her, and, in many ways, she is still the 15-year-old girl whose disturbed father chose to commit suicide, on her birthday, in her favourite park. She is struggling to look after that girl, to console her, to calm her.

He had already tried to gas Marie in his car, a few months previously, using pipes from the exhaust through the window. Things happen. But now, nearly 50, she does not want to sleep in other people's beds; and she is tired of being relocated to another unit or hostel every few weeks or months.

Marie can name the good things in her life. "Three lovely children" and a husband she lost but who is still her best friend. They speak on the phone. He is very wise, she says: he has money, their three children, and a settled life; but she never asks for any handouts.

Marie was asked: "What do you see in the eyes of people when you're selling The Big Issue?"

"Fear," she said. "I just see fear. There but for the grace of God, that sort of thing."

Later that day, I heard of a Big Issue seller outside Charing Cross Station. He said that he had once watched Russell Brand walk past him without stopping, and he was upset. So he called out: "Here, Mr Brand!" The comedian turned round and walked back to him.

"Sorry, mate, I didn't see you."

"No one ever does," the seller replied. Mr Brand bought a copy, and then journeyed on.

The Charing Cross seller was asked: "Why don't people see you?"

"Fear," he said, using exactly the same word as Marie.

As any therapist knows, we do not see inside us what we fear. If I fear being an angry person, for instance, I won't see my anger. And on the street, if I fear the collapse of my fragile life, I will try not to see the ones who have no front door, no resources, no hope. As Mr Brand said: "Sorry mate, I didn't see you."

Simon Parke is the author of A Psychiatrist Screams (DLT, 2013).