There are very good reasons to be optimistic.

Scientific research has come up with a long list of benefits to being optimistic. Here are just a few:

1. Optimism is associated with better health and a longer life.

2. Research  has shown that practicing optimism and gratitude causes (not just correlates with) an increase in happiness.

3. The army teaches soldiers to be optimistic because it makes them tougher and more persistent.

4. Being socially optimistic — expecting people to like you — makes people like you more.

5. Expecting a positive outcome from negotiations made groups more likely to come to a deal and to be happy with it.

6. Optimists are luckier. Research shows by thinking positive they persevere and create more opportunities for themselves.

7. Optimistic salespeople are more successful.

The list goes on and on. Being optimistic is one of the 10 things I recommend you do every day and something associated with great lives.

On the flip side, UPenn professor and happiness expert Martin  Seligman explains pessimism is very often a negative:

Research has revealed, predictably, that pessimism is maladaptive in most endeavors: Pessimistic life insurance agents make fewer sales attempts, are less productive and persistent, and quit more readily than optimistic agents. Pessimistic undergraduates get lower grades, relative to their SAT's and past academic record, than optimistic students…["Countering Lawyer Unhappiness: Pessimism, Decision Latitude and the Zero-Sum Dilemma" from Cardozo Law School Jacob Burns Institute for Advanced Legal Studies]

But it turns out many of the common methods for becoming more positive are bunk. Standing in front of the mirror saying cheery things doesn't help.

Pessimists can in fact learn to be optimists, and not through mindless devices like whistling a happy tune or mouthing platitudes ("Every day, in every way, I'm getting better and better"), but by learning a new set of cognitive skills… We have found that merely repeating positive statements to yourself does not raise mood or achievement very much, if at all. [Learned Optimism]

So are we doomed if we're not naturally optimistic? Don't worry, Frodo, we'll get you back to the Shire.

Here are the four steps that can turn pessimists into optimists — or even make mildly positive people very positive.

The three P's

It all comes down to what researchers call "explanatory style." When bad things happen, what kind of story do you tell yourself?

There are three important elements here. Let's call them the Three P's: permanence, pervasiveness, and whether it's personal.

Pessimists tell themselves that bad events:

1. Will last a long time, or forever. ("I'll never get this done.")

2. Are universal. ("You can't trust any of those people.")

3. Are their own fault. ("I'm terrible at this.")

Optimists, well, they see it the exact opposite:

1. Bad things are temporary. ("That happens occasionally but it's no big deal.")

2. Bad things have a specific cause and aren't universal. ("When the weather is better that won't be a problem.")

3. It's not their fault. ("I'm good at this but today wasn't my lucky day.")

Seligman explains:

The defining characteristic of pessimists is that they tend to believe bad events will last a long time, will undermine everything they do, and are their own fault. The optimists, who are confronted with the same hard knocks of this world, think about misfortune in the opposite way. They tend to believe defeat is just a temporary setback, that its causes are confined to this one case. The optimists believe defeat is not their fault: Circumstances, bad luck, or other people brought it about. Such people are unfazed by defeat. Confronted by a bad situation, they perceive it as a challenge and try harder. [Learned Optimism]

And when good things happen, the situation reverses:

1. Pessimists think good things will be short-lived, are rare and random.

2. Optimists think good things will last forever, are universal and of their own doing.

What's the ultimate result of this? Pessimists often quit. Life feels futile. And when life feels futile, you stop trying and frequently get depressed.

So now we understand the kind of thinking that underlies these positions… but how do you go from one to the other?

Research shows you should act like a crazy person… Okay, I'll be more specific...

Eric gets specific in the rest of the article:

http://theweek.com/article/index/265844/how-to-be-optimistic-according-to-science