If I Knew Then Advice on careers, finance, and life from Harvard Business School's Class of 1963

Perhaps most important is to have lots to do. It doesn’t matter what it is, but whatever you do in retirement should take a lot of effort. For me, it was house-building and ultra-running.

Be sure to keep up on exercise, with a healthy lifestyle. Try to get at least two hours of aerobic exercise each day. Be very careful about diet. (Editor’s note: Rich ran his last marathon in April 2013, at age 81.)

Before the wedding, make a deal about what type of life you expect to lead. Be willing to argue about things openly and even often. 

Hang out with your kids a lot, even if it means missing work opportunities. Give your kids the best schooling you can. Exercise together.