A lover of original headlines, I’ve occasionally fantasized about writing a column entitled “What happens when a one-pillow woman marries a two-pillow man?” That situation – true in my own case – could well serve as a metaphor for the large or small disparities that emerge when two people set up home together.Among the differences that make themselves most felt are those relating to basic mental posture.For example: Your view of life tends to the positive, looking on the bright side and seeing the proverbial glass half-full, while your partner’s approach is to focus on the real and potential downside of things, tending to bemoan the glass half-empty.Here too, I am rich in experience – but let’s leave the personal finely balanced on those lopsided bed pillows and turn our attention to the intriguing question of where optimism, or its opposite, comes from.For example, are optimists born or made? Science holds the belief that about half of one’s optimism comes from one’s DNA and half from one’s environment – which seems to make sense. If your parents, or even one parent, saw the world as a place of disappointment and failure, it stands to reason that you would incorporate at least some of this attitude into your developing psyche.In contrast, I have written about my surprise when I once asked Uri Avnery, founder of the radical left-wing Gush Shalom peace bloc, how he could maintain his sanguine view of the prospects of peace between Israelis and Palestinians in the face of depressing realities on the ground. Instead of the reasoned political exposition I expected, he answered: “I’ve always been an optimist, ever since I was a boy.”WINSTON CHURCHILL is reported to have declared that “a pessimist sees the difficulty in every opportunity, while an optimist sees the opportunity in every difficulty,” and he probably meant just what he said when he said it. But modern experts aren’t viewing optimism vs pessimism as a simplistic dichotomy of good and bad attitudes to life, rather as two different strategies for coping with a complex and unpredictable world. As one thoughtful blogger pointed out: The proverbial glass isn’t the static entity it is usually depicted as being, with a horizontal line dividing the part that is full from the part that is empty. On the contrary, its contents are “a churning, swirling mess” in which “liquid sloshes from side to side in agitation, spilling out over the top, and leaking from a hole in the bottom.”In other words, life is messy, and both optimists and pessimists develop different methods for managing this disequilibrium. Sometimes optimists can fall flat on their faces, and pessimists triumph. There is no “one size fits all” solution to life’s challenges.SIDE BY SIDE with the slew of self-help books and articles reminding us that pessimism damages our bodies and minds by creating stress, anxiety and depression and showing us how we can become ever more optimistic, experts are now decrying an excess of optimism and saying that a balanced perspective on life needs a healthy streak of pessimism – which, counter-intuitively, can lengthen our lives by prompting us to be more cautious and responsible in our actions.“Both optimists and pessimists contribute to society,” noted George Bernard Shaw. “The optimist invents the aeroplane, the pessimist the parachute.”Churchill himself, in his sober vision of where “peace talks” with Adolf Hitler were heading in the late 1930s, evinced a pessimism that history has resoundingly justified.Pollyannas may buoy themselves up for a time, but reality intrudes sooner or later. If someone spits at you, you can say it’s raining, but they might move on to throwing stones. If you then dismiss these as hail, you are more of a denialist than an optimist.CALLING NECESSARY pessimism “healthy realism” might help avoid over-optimism, for example when faced with someone who is ill. Many people are uncomfortable in the presence of serious illness – perhaps projecting it upon themselves – and may brightly deny a condition which is obvious to all, including the patient, in the belief that they are “cheering them up.” Cognitive psychologists have suggested, moreover, that excess optimism can cause family members of the critically ill to be unrealistically hopeful, which could affect their decisions about a patient’s care.One recent study revealed that older adults who held a dim view of their futures actually lived longer and healthier lives than those with rosy outlooks because they might have been more cautious and thus adopted a healthier lifestyle. Modest, defensive expectations could protect older people when health losses occur, leading to more satisfaction with their current circumstances. In other words, by predicting the worst, the reality experienced by older people in the study seemed not so bad by comparison. All this seems to avoid the question of happiness, and maybe happiness is a bit of a tall order, for younger people as well as older ones. Nevertheless, given the choice between a rosier outlook with more joy of life, and a few more “cautious” years on earth, I wonder which option most of us would choose.PSYCHOLOGISTS say that a measure of pessimism can prevent people from becoming too confident and overly trusting. And thoughtful pessimists who don’t just wallow mutely in their pessimism but are able to come up with reasoned arguments to support their negative view can inject a cautionary note when it is needed.I am far more impulsive than my husband, and push to act quickly on decisions once they are made. More than once, however, his pessimism concerning some course of action has held me back from indulging in expensive purchases that would have been wrong for our needs.Some research suggests that excessive optimism about one’s circumstances can thwart emergency-preparedness efforts – which speaks loudly to the Israeli tendency to declare “It’ll be fine” (hakol yihye b’seder) instead of relating to the threat of earthquake or enemy attack via precautionary measures like storing water, getting emergency lighting and keeping essential items close by.HISTORY’S MOST noted pessimist is the 19th-century philosopher Arthur Schopenhauer, who elevated will above reason as the driving force of human behavior. Believing that hunger, shelter, security and reproduction remain our prime motivations – and not some illusory goal of enlightenment – he considered daily life to be little more than suffering repeated over and over again, like that of the mythical Sisyphus condemned to roll a boulder forever up the hill, only to watch it roll back down again.History’s most famous optimist is the German intellectual Gottfried Wilhelm Leibniz, one of the great 17th-century rationalists. Applying his rigorous logical framework to the entire cosmos, he concluded that our universe is, in a narrow sense, the best possible one God could have created – leading to our use of the phrase “the best of all possible worlds.” Leibniz was mocked by Voltaire, who declared that “optimism is the madness of insisting that all is well when we are miserable.”WHETHER WE are essentially optimists or pessimists may indeed be a question of our genes, and opinions differ as to whether optimism can be “learned.”Mostly, I think, it can’t. On the other hand, the exercise of healthy realism – or cautious pessimism – is something we might all practice to our benefit, in our turbulent region especially.