“I sometimes laugh because here I am, sitting, looking at Excel spreadsheets and talking and worrying about margins. How have I become that person?” Like many creatives, Tina Roth Eisenberg, aka Swiss Miss, didn’t think sales spreadsheets would become part of her day-to-day. But the New York-based entrepreneur and blogger has managed to turn not one but five side projects into successful, profitable businesses. First, there’s her popular design blog, Swiss Miss, which averages…