Be happy, be upbeat, stay positive; it’s the modern philosophy of life, as shown by that master of motivational messaging, David Beckham. Even in the depths of defeat and the trauma of public resignation, he managed to declare: “I have lived the dream.” But amid this drive to be shiny, happy people, psychologists are cautioning that ignoring life’s grimmer side can damage our mental and physical health. Where reality’s concerned, we shouldn’t keep bending it like Beckham.

There’s no denying that positive thinking can be linked to a host of benefits, such as a greater sense of control over our lives and a stronger immune system. Thoughts are powerful determinants of mood and behaviour, so being optimistic can keep you striving after a challenging ambition, and keep your stress-hormone levels lower. But this link has made society embrace optimism as a tempting cure-all, with a flood of happiness-promoting books, columns and TV series, such as the recent Making Slough Happy on BBC Two. Where once we had the stiff upper lip, now we have the fixed smile. And this can be just as harmful.

Janet Zinn, 46 a clinical social worker, has given up trying to embrace the orthodoxy of positive thinking. In her private life as a busy parent and in her professional practice, she had completely adopted the mantra that positive thoughts produced positive results. “I felt that anger, jealousy and hate were negative and should be eradicated,” she says. Life became a perpetual effort to be upbeat and she turned into a self-confessed positive people-pleaser, too: “I thought that if I wasn’t happy it meant there was something wrong with me.”

Her life was fulfilling enough, but there were times when she felt dark and angry, which made her feel guilty. To achieve a state of lasting positivity she became a serial attender of groups and conferences on the “power of positive thinking”. But rather than boost her happiness, they left her feeling like a fugitive from her negative feelings. “In the end, I knew I wasn’t dealing with what was real,” she says. So she decided to explore her “shadow side” and to accept her negative thoughts. “Many issues that used to trouble me no longer do,” she says.

Forcing an optimistic outlook can hold us hostage to images of perfection that can exacerbate underlying symptoms of depression and anger. Studies show that people who deny their negative feelings are more likely to fall ill and take longer to recover from trauma and loss.

This is especially true for women, who tend to repress anger as unladylike: research by Michigan University linked chronic repression of anger to heart disease and cancer in women. Other studies, such as one by Harvard School of Public Health in Psychosomatic Medicine this year, show that men who express anger in a moderate fashion have a lower-than-average risk of stroke and coronary problems.

Dr Julie Norem is on a crusade against relentless positivity. She cautions that promoting optimism encourages people to believe that they can eradicate anxiety and negative thoughts. “Unless you’re a psychopath, that’s not going to happen,” she says. Instead, she argues in her book The Positive Power of Negative Thinking (Basic Books) that we should foster a strategy called “defensive pessimism”.

Defensive pessimists are not depressive pessimists. They are able to use their depressive thinking productively; they use the juice of their anxiety by mentally rehearsing all that can go wrong. This negative thinking propels them towards their goals and helps them to feel more in control, claims Dr Norem, a psychology professor at Wellesley College, Massachusetts. She says that defensive pessimists are excellent troubleshooters because they are aware of all that may go awry and have a realistic idea of their weaknesses. They are prepared, and this preparation prevents anxiety from overloading them.

Her research is helping to reinvent negative thinking as “pretty positive”. She says that the primary response she gets when addressing lay audiences is gratitude, together with sighs of relief from defensive pessimists who finally have been told that they don’t need to be fixed. Indeed, many of Dr Norem’s studies show that when you take away a defensive pessimist’s strategy, including that key component of negative thinking, his or her performance suffers. “It is hard to go against the whole positivity movement but, for someone who is a natural pessimist, faking optimism doesn’t work,” she says.

She adds: “We tend to grossly underestimate the disadvantages of optimism, which can include overconfidence and positive self-bias that make it harder for optimists to learn from their mistakes.” Optimists also tend to absorb only good news and are more likely to blame others when things go wrong. No strategy is perfect, though, and defensive pessimists have their drawbacks, including a tendency to alienate people with their insistent focus on potential problems.

Jung famously claimed: “I’d rather be whole than good.” He believed that the secret of wholeness was “hidden in the dark” and declared: “One does not become enlightened by imagining figures of light, but by making the darkness conscious.” Reflecting on the darker side of our experience can allow for greater self-acceptance and self-esteem, better health, less denial, and an enhanced ability to handle life’s challenges effectively.

All this helps the defensive pessimist to make lemonade out of life’s lemons, precisely because they embrace the sour bits.

Dr Lisa Nastasi is a clinical psychologist specialising in wellbeing

Are you a defensive pessimist?

Think of a situation where you want to do your best. It may be related to work, your social life, or any of your goals. When you consider the following statements, think about how you prepare for that kind of situation. Rate how true each statement is for you, giving yourself points from 1 to 7: ie, Not true at all of me, score lower points; Very true of me, higher points.

Add up your scores for all the above. Possible scores range from 12 to 84; higher scores indicate a stronger tendency to use defensive pessimism. If you score above 50, you would qualify as a defensive pessimist in Dr Norem’s studies. If you score below 30, you would qualify as a strategic optimist. If you score between 30 and 50, you may use both strategies, or neither strategy consistently. How you score will be influenced by the kind of situation you were thinking about when you considered the statement because you might use different strategies in different situations.

Reprinted from The Positive Power of Negative Thinking, by Dr Julie Norem, with the author’s permission