Kay Hsu, global director at Instagram Creative Shop, talks about living with stage IV metastatic breast cancer, an incurable form of the disease that has spread to her bones. "People always say you're going to fight it, but it's not one of those things," she says. Someday, the doctors tell her, "the medicine will stop working." She also weighs in on the sheer volume of fascinating content on YouTube, what to wear to chemo (loose, comfortable clothing) and her ideal meal at McDonald's.