Maura Tierney Maura Tierney

Maura Tierney played a nurse-turned-doctor on ER, but the actress says she was afraid to go the doctor before her breast cancer diagnosis.

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"I was so, so scared of going to the doctor," Tierney tells Parade, speaking at length for the first time about her recent battle with the disease. "I felt something, and my boyfriend at the time made me go. He said, 'You've got to take care of this,' because I was afraid. That's one thing I will say: Don't be afraid to go to the damn doctor. Just go!"

Tierney will appear on Friday's Stand Up to Cancer telethon and will play a cancer patient when she returns to Rescue Me's final season. The actress is grateful that she was able to combat the disease through aggressive treatment.

"I was so lucky. I had insurance, I found a great team of doctors at UCLA, and I could afford not to work while I was getting treated," she says. "From the beginning my doctor told me, 'You're going to be okay,' and I chose to believe him. So there was always that in my head.

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"It's a life-changing thing to be in a position of needing help and being so lucky as to get it. And to feel like that's okay," she continues. "You can't just take care of everybody else all the time. That's almost as perspective-changing as the illness. For someone like me, that was kind of tough."Tierney also says that after her initial surgery to remove the tumor, her doctors discovered the cancer was more aggressive than they had believed. She says a decade earlier, her story would have been completely different. "They would have patted me on the head and told me, 'You're cured,' and I would have died of breast cancer," Tierney says.Tierney says she isn't far enough away from her treatment to fully process what she's gone through — or what her next steps will be in spreading awareness about the disease.

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"There's this tendency for people to put on to you how they think you should be or what they think you should feel. The truth is, I had my surgery, and I have two more months on this one drug," she says. "I haven't figured out where I want to focus my energies to help others, and I don't know what kind of wisdom to drop on anybody yet — except for, you know, [doctors] can help people now."I feel an immense sense of gratitude, but sometimes I think there should be room for more gratitude [in me], because I can still be bitchy in the morning."