Stow your scowl. If you want to raise successful children, start showing optimism on a regular basis.

"Our beliefs and attitudes spill over to our kids," educational psychologist and parenting expert Michele Borba tells CNBC Make It. "If pessimism always builds and it becomes personal, permanent, or pervasive, it robs our kids of hope."

The problem: 78% of Americans aren't confident that life for their kid's generation will be better than it has been for them, according to a March survey from The Wall Street Journal and the University of Chicago.

It's understandable. School shootings, political animosity and a worsening climate crisis don't bode well for the future.

But that pessimism could become a self-fulfilling prophecy, Borba says: When it comes to raising children, your attitude as a parent is contagious. An optimistic outlook can help kids thrive, while pervasive negativity can cause them to lose interest and hope, research shows — creating a huge obstacle between them and a happy, successful life.

Here's why, and how Borba recommends training your brain to be more optimistic.

Children need optimism to thrive

Optimism flips a simple switch in kids' minds, Borba says: They start viewing challenges as obstacles to overcome, rather than excuses to turn around and go home.

Pessimism can be difficult to avoid in today's world, where people are "just getting bombarded with bad news" every day, Borba says. But when parents get stuck constantly worrying about negative news, their kids tend to exhibit more anxiety and stress.

"I think it's one of the reasons why we're seeing such a huge mental health crisis in our children," Borba says.

That makes showcasing your optimism all the more important, especially for ensuring that kids can handle life's ups and downs without losing hope of attaining happiness and success.

"That's probably one of the highest correlations of success," Borba says. "It's a child who says, 'I'll just keep chunking it and keep on doing it' ... As opposed to: 'Why should I bother and try?'"

Parents might need to tailor their own outlook

Even if you make an effort to not voice your concerns to your kids, your anxiety can rub off on them nonetheless.

"It's not just the eavesdropping on what we say," Borba says, noting that older kids especially can pick up on physical cues that you're stressed or worried. "Very often, teens say the most important thing is how we look."

That means you need to start by examining your own habits. Turn off the television when you find yourself stuck in a negative news spiral. Try repeating positive affirmations on days when the stress of the world is getting you down, a tactic that psychologists say can help reduce stress and boost self-esteem.

Remember that optimism can be learned and taught — which is good news for both parents and children.

"The next time something happens, [you can say] 'That's OK, we've got this.'" Borba says. "If you keep saying it, you're actually having your kid eavesdrop on your management strategy. And the most amazing thing is very often they pick it up, and now they have a way to talk back to the worry themself."

Promoting optimism doesn't mean living in denial

Practicing optimism doesn't mean being unrealistic or blind to the world's many real problems. Turning off the news isn't about living in denial, Borba says: It's about recognizing when a behavior boosts your anxiety, and not over-indulging in it.

"Our goal is not to raise a Pollyanna," Borba says, referring to the sort of person who is blindly optimistic or positive. "The reality we face is: It's a tough, unpredictable world."

Be open with your children about sad or scary things happening in the world, Borba says. Chances are, they're going to learn those things anyway — whether on TV, social media or from friends. Frame those conversations in ways that acknowledge the tumult without sounding hopeless, she recommends.

You can also actively inject optimism into your kids' outlooks. That could mean going around the dinner table to discuss positive things happening in your daily lives, or making a point of sharing good news from around the world.

Lastly, acts of service as a family can help by reminding kids that they can improve other people's lives, even by volunteering locally. Volunteering can help your community, and research shows it can boost your own mental health.

"Help your children see that they can make a difference," Borba says. "Once they begin to do that, they develop an incredible mindset [that] says, 'I've got this,' because they're beginning to recognize they can be little changemakers."

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