Maybe I would have made it through my 20s without him. But, to be honest, I can't imagine how.

I’m so grateful for modern medicine.

Without it, this guy, my grandfather, would have died in 1984, when I was 10 and he had his first heart attack.

Instead, he thrived for another 20 years, until he was 93 and I was 30.

I loved him like crazy.

I knew him a little when I was a kid, but he wasn’t warm and cuddly. He and my grandma were always heading somewhere glamorous—a symphony hall, a ski resort, a book discussion at their social club—and weren’t so keen on playing Barbies or dress-up with me. When he was around, he seemed grumpy and tense.

But then, when I was in college, our relationship finally bloomed.

Early in my freshman year, I was struck with debilitating anxiety, and my grandpa shocked me by revealing that he’d spent the past 50 years trying to tame his own mental illness. At one point, in the late 1950s, it had gotten so bad that he’d pulled my mom and her brother out of school and moved the family to Europe.

Over the next decade, he told me his story, and his symptoms, it turned out, were eerily similar to mine. Day and night, he was plagued by vivid and terrifying worries that made no sense but still felt true; day and night, his palms sweated, his heart raced, his stomach heaved.

All the same, he’d managed to survive, and the more I talked to him, the more I realized I could, too.

Maybe I would have made it through my 20s without him. But, to be honest, I can’t imagine how.