LYNNWOOD — Being good at roller derby takes determination, discipline, perseverance and courage.

Living with multiple sclerosis takes all of that and more.

For Stephanie Miller, the same traits that have helped her excel at roller derby, a sport she loves, have also helped her face a disease she detests. Stricken six years ago, the 30-year-old Miller vowed not to give in to MS, and she has since used roller derby as a way to stay strong both physically and emotionally.

“I refuse to let MS control my life,” said Miller, who lives in Lynnwood. “And I refuse to let it tell me what I can and cannot do.”

There are days, she admits, “when the MS rears its ugly head and then it’s difficult. I might have a five-minute pity party and go cry in the corner, but then I get back to (my daily activities). I have to be bigger than MS because I can’t afford not to be.”

Even on days “when I’m willing my body to cooperate, I don’t want to give up because I’m bigger than this.”

Miller, who skates under the name “Blow Bye,” woke one morning in January of 2009 with blurred vision in her left eye. It was, she thought, the onset of a migraine headache. But the symptoms became worse, and a series of subsequent tests — including a CAT Scan and an MRI — revealed a lesion on her brain, leading to a diagnosis of MS.

The pronouncement was “a huge blow for me,” she said. “It was pretty depressing.”

But over the next several months Miller began to fight back. She visited a naturopath who recommended dietary supplements. She became more committed to proper nutrition and rest. And she decided to improve her fitness, which led to roller derby.

She and her husband, Dan, who met while roller skating, were living in Abbotsford, B.C., at the time. Miller went one day to watch a roller derby match, was immediately intrigued and soon signed up for a team. She skated in Canada for two years before the couple moved to Lynnwood in 2012, and at that point she joined the Everett-based Jet City Rollergirls, where she is now in her third full season.

Though never a top athlete in high school — “I was more of a bookworm,” she said — Miller has a passion for roller derby. At 5-foot-4 and 127 pounds, she is smaller than many skaters, “but what I don’t have in size, I try to make up for in other ways. I try to see things before they happen, and I try to outsmart (opponents) when they outsize me.”

But as much as she loves the game itself, there is equal joy in the camaraderie. Miller, who skates for Camaro Harem in the four-team league, said the other Rollergirls have been “beyond supportive. If I need to sit out, they let me sit out. If I’m having a bad day, they’re the first to give me a hug. It’s just love. Yeah, we hit each other on the track, but we love each other.”

Niki Desautels of West Seattle, who skates as Eva Derci, has been a teammate since Miller joined Camaro Harem in 2012. At the outset, Desautels said, Miller was “pretty private” about her disease. It took months before Desautels found out, “and I was surprised to hear about that. (MS) is a tough thing that you don’t usually associate with playing roller derby.”

Though Miller has sometimes excused herself during strenuous practices, “it’s been no more than some of our other skaters that are not dealing with anything like this,” Desautels said. “She’s not going to let this hold her back at all. She’s always at practice, she never misses a game, and she’s one of our top players. … She just has the mental strength you have to have to do this.”

Because MS is an insidious disease — crafty in its ways, cruel in its intent — it is impossible for Miller or any other sufferer to know the future. Symptoms can be manageable for many years and then suddenly become more severe. The harsh truth is that MS proceeds at its own pace without compassion and, as yet, without a cure.

Twenty years from now, “I could still be where I am right now,” Miller said. “Or I could be in a wheelchair. You can’t predict because with MS every single case is different. That’s why I’m trying to live it up as much as I can, while I can. I’m not going to let this get me down because I’ve seen people who’ve taken that road and I’ve seen how fast MS can take them over.

“I’m going to skate until I can’t skate anymore,” she said. “I’m only 30 years old and I still have a long life ahead of me. This is just some stupid disease, and I’m not going to let it be an excuse for me to give up.”