About four days into my first meditation retreat, I started crying. Not little droplets of tears, but great, big, uncontrolled sobs – it felt like I was throwing up wave after wave of stale sadness. I'd expected the long days of sitting to be boring, annoying, physically demanding and (with a bit of luck) illuminating, so to find myself repeatedly breaking down into a noisy heap of grief came as a shock. These spontaneous outbursts of wailing continued throughout the month-long programme – it says much for the teachers' equanimity that they didn't chuck me out. So when would-be practitioners ask about the benefits of meditation, I tend not to give a straight answer. Will it help you be less stressed? Reduce your pain? Make you think more clearly? Stop you from eating too much? Well, maybe it will help with all of those things, but there's no guarantee, and even if it does, you might find there are other effects too, like finding yourself questioning your career and relationships, or feeling increasingly unwilling to fit in with whatever herd you usually hang out with. You might discover that meditation opens you up to powerful surges of rage, disappointment, doubt, yearning or regret that you didn't know existed. Of course, none of these things are certain either, but they do happen. Most of them have to me, at some point over the last 10 years. A lot of people now come to meditation having read reports on the virtues of mindfulness. Last week there was one claiming it can ward off ageing, and one suggesting meditators make more rational decisions. A month ago mindfulness was declared more effective for pain relief than morphine (maybe, but I still wouldn't fancy the dentist's drill without an injection), while it's also being said to increase grey matter in the brain, ease the fear of dying, and help US army troops operate effectively in a war zone, as well as protecting them from post-traumatic stress. Two new books are out in May, offering meditation plans as a proven path to wellbeing. Such reports and regimes are genuinely helpful – I've written and enthused about similar ones myself – but collectively they can start to give the impression that meditation is the cure for all life's ills, and that if we could just sit down and follow the breath, problems and pain will fall away. Ten or 20 years ago, meditation suffered from an undeserved association with flaky new-ageism; today there's a danger of another unhelpful image – mindfulness as hassle-free, quick fix. As anyone who's actually sat down to practise knows, this is a consumer fantasy. Mindfulness has a great many benefits, but they tend to come as a by-product of getting up close to unpleasant experiences like pain, turmoil, and "negative" thought patterns. Striving to avoid unwanted aspects of ourselves and our lives creates stress – by facing them openly in meditation, we give ourselves a chance to relate to suffering more skilfully, with confidence and compassion. This means we have to experience and befriend our sadness, anger, physical pain and so on. When we omit to mention this, and fixate only the "positive" results of meditation, we risk passing on a partial description of the path, which involves being present to every aspect of life – what Jon Kabat-Zinn calls, after Zorba the Greek, "Full Catastrophe Living". When mindfulness meditation first came to the west, its Buddhist context offered a counter-balance for the tendency to turn it into a goal-achieving mental workout. The Zen teacher Suzuki Roshi used to instruct his students to "die over and over again" as they sat still in zazen, until their desire for enlightenment began to dissipate and they could begin to appreciate a taste of it. If you thought you were going to get something from meditation, then you weren't getting it. As mindfulness teaching expands beyond these lineages, there's an ongoing risk that a rich and challenging spiritual practice will be reduced to a lightweight lifestyle add-on that's more palatable to our cultural taste – ironically, this would probably negate the benefits that everyone's getting so excited about. Meditation is deep work with an uncertain outcome. It's worth it, but it isn't always comfortable.