I am sitting cross-legged on the floor in a large hall, surrounded by strangers. Sweat is running down my face, and my thighs are bleating in agony. I'm trying to meditate but my mind keeps calculating how long I've been here (about five hours) and how long there is to go (about another 100).

It is the first day of my silent retreat in Gujarat, India. I am not allowed to talk throughout the 10 days. In fact, I am not allowed to do much at all: I can't make eye contact with my fellow meditators, or read, write, listen to music, exercise or do just about anything except sit here on the floor.

My reasons for signing up suddenly seem very foolish. Rather than it being a spiritual quest or an attempt to resolve deep-seated personal issues, I came here hoping for fireworks of the meditative kind. I have meditated intermittently for years, and I know that it works.

When I have occasionally managed to keep it up for more than a few days at a time, it definitely makes me a calmer, nicer person, and better able to sleep. On good days, I find it mildly pleasant, but there has always been something missing. Other meditators describe seeing colours, experiencing heightened states of bliss or developing a serene understanding of the complexities of life. That has never happened to me. So, in the hope of bypassing the years of steady effort I suspect may be required, I travelled to the Dhamma Sindhu centre to do a Vipassana retreat, the most extreme form of meditation I know.

Vipassana, which means "to see things as they really are", is an ancient Buddhist technique revived and popularised by a Burmese-born Indian, SN Goenka. His courses are taught in about 140 centres around the world, all of which observe the same schedule: wake up at 4am, meditation from 4.30am, breakfast at 6.30am, more meditation, lunch at 11am, meditation, dinner (two pieces of fruit and a cup of tea) at 6pm, meditation, a video talk by Goenka, and lights out at 9.30pm. The courses are free, although you are encouraged to give a donation at the end.

There are about 120 of us doing the Gujarat retreat, all but 10 of whom are Indian. The day before it starts, we queue to hand in books and mobile phones, before being shown to our single, cell-like rooms. The following morning, with just five hours of meditation under my belt, I am already experiencing misgivings.

I had been prepared to hate it at times, even occasionally to regret coming, but I hadn't expected it to be a constant struggle. Worse than the silence, by far, is the pain. No amount of meditation I've done before could prepare me for sitting on the floor for 10-and-a-half hours a day. I try everything: more cushions, fewer cushions, two small cushions under my knees, a firmer cushion tilted under a softer cushion, a cushion on my lap to rest my hands on. Nothing helps.

After two days, gaps start to appear in the meditation hall. People are dropping out. We have been warned that days two and six will be the most difficult, so I moderate my expectations and prepare for it to be grim until day seven, when, surely, there will be joy?

In the meantime I suffer. The Vipassana technique involves systematically moving your attention around your body, noticing physical sensations but not reacting to them. If you find your mind wandering, you are told to observe your thoughts and let them pass without joining the conversation. But that is easier said than done. Work, relationships, my parents' deaths, the novel I had been half-way through, Downton Abbey: all these kept popping into my head.

Every night Goenka encourages us from the television screen, promising a happier, more harmonious life if we learn to welcome both pleasure and pain. "Accept the sensations as they arise, no craving and no aversion, they will pass," he keeps saying.

Day six is no improvement, and several more people leave. Day seven is awful. As well as the pain, there is the boredom. I realise how much I rely on external narratives to get me through the day – work, novels, films, gossip, Twitter, news, whatever. Here it is just me and my daydreams, which are embarrassingly transparent. By now I know my search has failed.

"The purpose of Vipassana is not to experience pleasurable sensations but rather to develop equanimity towards all sensations," Goenka says. "Your progress is measured only in how far you are able to face life's vicissitudes with equanimity, nothing more."

There is a lot of talk about the vicissitudes of life, and being equanimous in the face of adversity, all of which I find rather quaint. I can imagine how useful that might be, but mostly I'm just counting the hours until I can leave.

Then, after lunch on day eight, everything changes. I enter another dimension. It is as if the boundaries of my physical body have dissolved, setting every molecule free to fly around the room. Everything is glowing red; everything is joyful. It is like the most intense drug-induced out-of-body euphoria, but calm, with no anxiety, no doubt.

So this is it, I think. I picture my fellow meditators sitting quietly around me. Are they feeling the same thing? Why has it taken me so long? I don't understand what is happening and I don't feel the need to try. It could be a purely chemical reaction to depriving my brain of pleasure for so long. It doesn't matter.

The sensations last, with varying intensity, for the remainder of the retreat. On the afternoon of the 10th day the silence is lifted and I try to speak to the others about their experiences, keen to find out if they had these glorious out-of-body sensations too.

A Polish woman, who is in a cell near mine, seems a bit embarrassed by my questions. "That's not what it's about," she says, somewhat dismissively. A Filipino man on his fifth Vipassana retreat tells me that he has never felt any bliss, but doesn't mind because meditating has changed his life so much.

Back home, my friend Stella, who has done a Vipassana retreat, is more forthcoming. "Oh, you had the orgasms," she says. "Yes, I had those too, but not everyone does. They're really not important."

She is right. What I have to admit afterwards is that sensation-seeking is the very antithesis of meditation. It is not about the colours or the bliss; rather it's about strengthening the muscle that helps build resilience. A steady practice that leaves you a bit better equipped to pause before lashing out, to rise above perceived slights and not be put off by the usual setbacks. A little more able to face life's vicissitudes with equanimity, as Goenka would say.