You must learn to live with the fact that you will make mistakes—lots of mistakes—and that you will learn from them. Mistakes are in fact a great source of strength; making mistakes is analogous to building muscle in athletic training. Think about it for a minute: how does an athlete get stronger? By pushing to the point of failure. You do, say, three pull-ups and fail on the fourth. The body point of failure. You do, say, three pull-ups and fail on the fourth. The body adapts and gets stronger and the next time you can do four pull-ups, and fail on the fifth. The next time out you can do five pull-ups, and fail on the sixth, and so on.

A strength, on the other hand, is an “activity that makes you feel strong.” This sort of activity possesses for you certain definable qualities. Before you do it, you find yourself actively looking forward to doing it. While you are doing it, time seems to speed up, one moment blurring into the next. And after you’ve done it, while you may be tired and not quite ready to suit up and tackle it again, you nonetheless feel filled up, proud. It is this combination of three distinct feelings—positive anticipation beforehand, flow during, and fulfillment afterward—that makes a certain activity a strength. And it is this combination of feelings that produces in you the yearning to do the activity again and again, to practice it over and over, to thrill to the chance to do it just one more time. A strength is far more appetite than ability, and indeed it is the appetite ingredient that feeds the desire to keep working on it and that, in the end, produces the skill improvement necessary for excellent performance.

Somehow, on the best teams, the team leader is able not only to identify the strengths of each person but also to tweak roles and responsibilities so that team members, individually, feel that their work calls upon them to exercise their strengths on a daily basis. When a team leader does this, everything else—recognition, sense of mission, clarity of expectations—works better. But when a team leader doesn’t, nothing else that he or she tries, whether in the form of money or title or cheerleading or cajoling, can make up for it. Ongoing work-strengths fit is the master lever for high-performance teams: pull it, and everything else is elevated; fail to pull it, and everything else is diminished.

And because competencies are unmeasurable, it is impossible to prove or disprove the assertion that everyone who excels in a particular job possesses a particular set of competencies. It is equally impossible to show that people who acquired the competencies they lacked outperformed those who did not—that, in other words, well-rounded people are better. These two statements together are the foundation for most of what companies do to develop the talents of their people, yet each of them is unfalsifiable—you will find no academic papers in any peer-reviewed journal proving the necessity of possessing certain competencies, and no proof that acquiring the ones you lack nets you any increase in performance. Both of these assertions, despite the good intentions that created them, are conjured from thin air—and we can never know if they are correct.

The 20 percent number was a threshold, which is to say that a little love goes an awfully long way: when you can deliberately weave your red threads throughout the fabric of your work you’ll feel stronger, perform better, and bounce back faster.

These red threads are your strengths. Typically we think of our strengths as what we’re good at and our weaknesses as what we’re bad at, and that our team leaders, or our colleagues, are therefore the best judges of both. But as we saw in chapter 4, this is not the best definition of either strengths or weaknesses. A strength is any activity that strengthens you (for Miles the anesthetist, keeping a patient hovering between life and death), and a weakness is any activity that weakens you, even if you’re good at it (for Miles, helping patients recover). “Performance” is what you have done well or poorly, and your team leader can be the judge of that. Team leaders and colleagues, however, can’t judge what strengthens or weakens you.