The human desire for companionship may feel boundless, but research suggests that our social capital is finite—we can handle only so many relationships at one time. Social scientists have used several ingenious approaches to gauge the size of people’s social networks; these have returned estimates ranging from about 250 to about 5,500 people. Looking more specifically at friendship, a study that used the exchange of Christmas cards as a proxy for closeness put the average person’s friend group at about 121 people.⁠ ⁠ However vast our networks may be, our inner circle tends to be much smaller. The average American trusts only 10 to 20 people. Moreover, that number may be shrinking: From 1985 to 2004, the average number of confidants that people reported having decreased from three to two. This is both sad and consequential because people who have strong social relationships tend to live longer than those who don’t.⁠ ⁠ _____⁠ ⁠ So what should you do if your social life is lacking? Here, ...