So, how can you plan for a successful, happy transition into the second half of your life? I'd like to offer six secrets:Who would have known Barbra Streisand foreshadowed the results of a scientific study when she sang her song "People"? But did you know that those lucky people also live longer? A study done in New Haven, Connecticut found that men and women who were socially active lived an average of two and a half years longer than those who were not. Other studies have found that social interactions have a significant effect in maintaining mental health, regardless of whether retirees live alone, live with someone other than their spouse, or are childless. Satisfaction in retirement is strongly correlated to the strength and number of your personal connections. It would seem that investing in building and maintaining friendships can reap far greater rewards than investing in stocks and... less