Carrie Classon’s, “Blue Yarn: A Memoir,” is available at Amazon, Barnes and Noble, and other fine stores. Learn more at CarrieClasson. com. I spent last week trying to be useful. I volunteered for a writers’ conference in San Miguel de Allende, Mexico, where my husband Peter and I stay. I love writers’ conferences. I love that people will travel from far away just to talk about writing, to meet other writers, to learn about writing, to listen to established writers and to eat. It was a terrific week, although it was tiring because I ended up as the designated conference sheepdog. Every event of this kind needs at least one sheepdog, and since I had fewer administrative and computer skills than other volunteers, I was happy to do it. Being a conference sheepdog is exactly like being a real sheepdog except, instead of sheep, there are lost writers wandering around and getting separated from the herd -- and I didn’t actually nip at their heels. Instead, I did my best to help them get…