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When a close friend has an intense interest or preoccupation, it often rubs off on me. For years, one friend was constantly bringing up what she called "the measurement problem" -- the idea that measuring an activity or trait you value (or choosing not to measure it) changes the way you act on it. "If you don't measure something, it's easy to ignore it," she explained. "And that can be a problem."

This idea struck me with such force that I made it one of my Secrets of Adulthood: "I manage what I measure." If I want something to count in my life, it helps to figure out a way, literally, to count it.

I have tangible proof of this: As part of my happiness projects, I keep a chart tracking all my resolutions; each day, I score myself on whether I've kept or broken them. I find that I'm far more likely to stick to a resolution when I set myself a task related to it -- and when I measure whether I do that task.