I was nervous about the second week of my trip, which I spent in Estonia. For the first time since being diagnosed with diabetes, I was completely on my own. I took a plane from Riga to Tallinn, Estonia’s capital. From Tallinn, I took a bus and a ferry to Saaremaa, an island off the western Estonian coast. Saaremaa is Estonia’s largest island. The land is mostly flat, punctuated by meteorite craters; the largest crater, known as Kaali Lake, is almost circular and filled with water. The one town on Saaremaa is Kuressaare, which...