Readers write us and say they would love to travel more but they are divorced or widowed. Most are women.      Stu is a fabulous travel partner, but I am here to tell you that I love, love, love traveling alone. It is true that I have been on my own quite awhile and traveled for work.  Over time, I got used to eating in restaurants by myself (I always took a book at first), and have experience hailing cabs and negotiating airports. But I am an introvert. I am also about to be 70.     I want to share what I’ve learned by traveling alone in hopes…