Having a mental illness doesn't mean you can't have a healthy relationship. 

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Psychotherapist Quinn Gee, M.S., of Washington, D.C., broke down what it's like to be in a relationship with a partner who has a mental illness in a viral twitter thread.

Gee recommends educating yourself about your partner's illness and their symptoms.

And know that when it comes to symptoms, everyone is different; there is no textbook definition that applies to everyone:

Let them know you're there for support—and ask, specifically, what support looks like to them, so you know what they may need.

She also has suggestions if both partners have a mental illness:

Gee also recommends couples therapy, if you think you would find joint sessions helpful. But perhaps the most important thing to keep in mind is:

And know that it's a process:

The takeaway?

Gee is right: When it comes to mental illness, you're not alone. In fact, a recent study shows you may be even less alone than you realize.

Earlier this year, researcher Aaron Reuben published a study in Journal of Abnormal Psychology on the prevalence of mental illness.

Rueben wrote about the results of the study for Scientific American, republished by Business Insider on Saturday, and noted, "most of us know at least one person who has struggled with a bout of debilitating mental illness. [...] New research, from our lab and from others around the world, however, suggests mental illnesses are so common that almost everyone will develop at least one diagnosable mental disorder at some point in their lives."

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Rueben and his team decided to track this by observing one generation of New Zelanders, "all born in the same town, from birth to midlife. We conducted in-depth check-ins every few years to assess for evidence of mental illness occurring during the preceding year."

They found that at some point in the subjects' lives, the number of people studied who developed some form of a diagnosable mental illness jumped to "well over 80 percent."

Rueben broke it down further:

Put another way, our study shows that you are more likely to experience a bout of mental illness than you are to develop diabetes, heart disease or any kind of cancer whatsoever—combined.

This doesn't mean that everyone afflicted was permanently suffering. In some cases, you can think of mental illness as having an ebb and flow, rather than the features of a typical physical malady. 

John Horwood, a psychiatric epidemiologist and associate professor at the Health Research Council of New Zealand told Scientific American "a substantial component of what we describe as disorder is often short-lived, of lesser severity or self-limiting."

This doesn't mean it's not difficult to experience. "Even short-lived or self-limiting disorders can wreak havoc on a person’s life," Reuben noted. Which is why Gee's advice is not only helpful, but given how widespread mental illness is, necessary.