We all have thoughts that invade our brains from time to time and mess with our moods. We all get down.

Whether it’s your job, your social life, your family, or something completely different, sometimes the negativity can be too much.

“We all have it. We all have it,” says Mark Reinecke, a professor emeritus of psychology and behavioral sciences at Northwestern University’s Feinberg School of Medicine.

Natalie Dattilo, PhD, a clinical health psychologist at Brigham and Women’s Hospital in Boston, agrees.

“Thoughts that we have that we would classify as negative or unhelpful are pretty normal. We all have thoughts that somebody might say, ‘Oh that’s kind of negative.’ “

Sometimes it is, and sometimes that’s just kind of an accurate description of a bad situation.”

But what can you do about those negative thoughts?

They may be common, but negative thoughts aren’t harmless or to be taken lightly. Research shows that having them over and over, while you have depression and anxiety, can lead to serious emotional and physical problems.

A bout of negative thinking now and then or a random negative thought here or there may not mean much. But having them over and over for a period of time can quickly overwhelm a person. Using words like never or always — “It’s always going to be like this,” or “I’m never going to be any good” — are a red flag.

Ruminating — dwelling on negative thoughts — can be dangerous.

“People often talk about thought loops and thought spirals, this sort of chaining of bad things,” Dattilo says. “It does tend to snowball. And that’s the part where it can become problematic.

“It’s less about the content of the thought, and more about the process, and the inability to let it go, having it run through your mind over and over and over again,” she says “Those tend to be negative for people. People are rarely ruminating on other things.”

How can you tell that the way that you’re thinking is doing more harm than good?

“Is it affecting your relationships? Is it affecting your work? Is it leading you to do things that are really harmful, like alcohol and drug use? Are the ways that you’re coping with it getting you into trouble? If they are, you probably need to talk to somebody,” Reinecke says.

“If it’s persistent, if it goes on for more than 2 weeks, if you just can’t get out of this cycle, you probably need to talk to somebody.

“If you have suicidal thoughts, and particularly if you make any behavior — you write a suicide note or pick up that bottle of pills in the medicine cabinet — you need to talk to somebody,” he says.

Reinecke suggests several ways to help break the grip of negative thinking. Many of the methods he suggests fall under the umbrella of cognitive behavioral therapy (CBT), a treatment that focuses on ways to change unhealthy ways of thinking and behaving.

“Sometimes the answer is right there in front of you,” Dattilo says.

Friends and family members can help by staying engaged with, and not withdrawing from, those who are wrangling with unhealthful ways of thinking. Acknowledging their point of view, maybe offering a sympathetic ear — “Well, sounds like you have a lot on your mind,” or “Do you think it would help to think about it like this?” — can be useful.

Certainly, professional help is always an option. The key to quelling harmful, negative thoughts may be more in how we think, rather than what we think.

“There’s a lot of people who tend to see the world [as] glass half-empty but believe that they’re fully justified in the way that they see it,” Dattilo says. “My job isn’t to necessarily argue with them about that, or to convince them to see the world differently.

“My question to them would be, ‘How does it make you feel to think that way?’ And if your goal is to feel better, or have better relationships, or to have more fun, ‘Does thinking like that help you?’ “