How many times have we been told that it is essential to have an optimistic attitude? Well, guess what, folks: If you read the latest issue of the Journal of Personality and Social Psychology (assuming your subscription is paid up), you’ll find a study conducted by three professors who conclude that a perennially positive outlook might just be overrated. As one of them told The Washington Post: “As a rule, you’ll get the advice that it’s better to be optimistic. But the truth is that it makes no difference.” In fact, according to co-author Don Moore, “Sometimes, it’s even worse.”

That’s because overconfidence can lead to debilitating disappointment and a big waste of time. Sometimes, Debbie Downer is right. Sometimes, the silver lining has nothing but clouds.

There now. Has this added a bounce to your step? Maybe not, but a can-do attitude must always be mixed with realism. As a matter of fact, it’s probably useful to put many of our expectations into perspective.

We are incessantly reminded to take care of ourselves, but what’s also healthy is this dose of truth I saw somewhere: “I eat a proper diet, exercise and get plenty of sleep. But still, I die.” That is not to say that we should lead a toxic lifestyle, but there is so much pressure to stay up late and be couch potatoes pursuing flabbiness that the motivation for being in shape is elusive.

There’s another study that demonstrates that, in spite of promises to reform, the food industry is still pumping out TV commercials that promote its unhealthy concoctions of addictive sugar, salt, high fat and low nutrition. The constant drumbeat of ads is aimed mainly at our kids, meaning that from childhood we learn seriously damaging lessons. Ultimately we don’t even comprehend the idea of healthy eating as we waddle into adulthood. Obesity is a national problem. So while we admonish everyone constantly that proper habits are beneficial, few can hear over the sound of their chewing potato chips.

Of course, the fat-cat merchants of fat are aided and abetted by those who make the laws in this country. The lawmakers, in turn, are aided and abetted in their nonfeasance by the wealthy special interests who make a mockery of our claim to have a “government of the people, by the people and for the people.” Sadly, that has become an empty promise and little more. We are a government for the highest bidder. Campaign pledges to protect the middle class fade away after Election Day almost as quickly as the middle class is disappearing. By almost any measurement, we are on a downward spiral — except for the shrinking group of those who hoard nearly all the nation’s riches.

And here we go again, with the leading candidates in both parties giving lip service to the plight of “everyday Americans.” At the same time, they cozy up to the powerful few who dole out strings-attached contributions in much the same way John D. Rockefeller used to throw dimes at the desperately poor.

Candidate Barack Obama represented himself as a new type of “post partisan” politician. So did George W. Bush; so did Bill Clinton. So did those before, and so are those running this time. What we’ve ruefully realized is that they’re all the same; they make promises they have no intention of keeping even if they could, which they can’t.

The differences in our political factions have become too great. Some of them are sincere, but many are just flames for the ambitious phonies to ignite, making problem-solving consensus almost impossible.

In the United States, the biblical admonition “let us reason together” is now an impossibility. As a result, the promises we hold so dear are becoming nothing more than still more cliches.

Bob Franken is a longtime broadcast journalist, including 20 years at CNN.