"Crying it out" is just mean for Mommy

We bought the book: the one everyone from a cousin in Canada to a friend in New Jersey recommended. Despite the fact that the man at the bookstore made fun of me for buying a book about managing a baby's sleep schedule ("I have a three year old and, even though I work at Barnes and Noble, I can tell you from experience that there's no book that can really help you here"), I bought the book. And I even read the book. There may be a dozen books on the living room bookshelf that I have never opened, but this book about a baby's sleep habits I did read. Even when the book's author implied that I have already failed as a parent, that Belle's sleeping will never be on track and Belle may likely grow into an ineffective adolescent and end up addicted to sleeping pills as an adult, I continued to read the book. When I finished reading, I reviewed the pages I'd dogeared and shared with Craig the sections I'd bookmarked. So, when Belle fussed and cried and cried and fussed and would not go to sleep this evening, even with her droopy eyes and even after she'd been fed and soothed, we decided to try one suggestion from the book: we let Belle "cry it out" for ten minutes. With the bedroom dark and Belle calm, Craig gently placed her in her crib. When she started to cry, he closed the door and noted the time. Belle's crying escalated to screaming and I had to sit on my hands while I watched the clock crawl from minute to minute until the the minutes had passed and I could go to her as we'd agreed. Finally, after ten excruciating minutes listening to Belle's unhappy cacophony of wailing, I raced into the bedroom. I found Belle in the far corner of her crib (she's become quite the crib roller) and immediately lifted her. She instantly quieted, calmed, accepted the pacifier, and fell to sleep sweetly in my arms. And then, perhaps from the anxiety of letting Belle cry for the first time, I cried. I lay Belle back in her crib and she's been sleeping since. When I left the bedroom, I cried to Craig and told him how hard listening to Belle "cry it out" was. It really seems just mean. I realize that I can't go to Belle every time she cries, and I know that Belle shouldn't get used to falling asleep on me, but it just feels so mean to voluntarily, intentionally let Belle scream. Did Belle get to sleep? Yes, after my crying began.