I'm a big fan of mistakes. In business, as in life, mistakes are how we learn. As infants, we learned to walk by falling over. We acquired speech by speaking gobbledygook that eventually evolved into language. And yet, when we grow up, we often become strangely awkward about our missteps. It's no accident that almost all business books are about successes—that's what we like to talk about. But it's the mistakes we learn from.

So what's your best mistake? One of mine occurred when I was in charge of an exhaustive (and exhausting) series of television programs: 13 shows designed to go out in one week. Of these, two were live broadcasts. Now, I'd never in my life produced a live show; all I knew was that they were really different and very demanding. It slowly dawned on me that I was out of my depth and that these shows were too important to be my first lessons.

So I went to my boss and explained the difficulty: I didn't have the experience, the expertise, or the time to acquire either. I needed help. At which point, he put his arm around my shoulder and came out with the immortal words: "All you really lack is confidence." And he then proceeded to talk me into persevering.

The shows were a fiasco.

Looking back, I realize now that he passed the buck and that that was the wrong thing to do. But I should not have accepted it. We all lack confidence sometimes—but there are times when our insecurity is completely justified. All the motivational speeches in the world cannot give you the ability to achieve goals for which you lack all the resources.

This mistake comes back to me repeatedly because I frequently sit in on management retreats, which are punctuated by motivational speeches and team exhortation. We can do it! If we only believe in ourselves! Self-belief can—and does—achieve a lot. But it is no substitute for resources, experience, expertise, and strategy. Just because you can talk yourself (and others) into anything doesn't mean you should.

I'll never forget coming home after the live shows, to be greeted by my partner: "What a stinker!" Remarkably, my boss later acknowledged that the stinker had really been his fault, not mine. But I had learned an invaluable lesson whose value far outweighed my ignominy.