OK, so there are two sides to this.
Yes, sometimes you have to act like you know what you’re doing until you get it figured out. Used as a TOOL — a bridge — this can be incredibly helpful to get you from where you are to where you need to be. It buys you some time. But there’s a catch, a danger: two, actually.
First, as anxiety-producing as it might be to weather a situation where you don’t know what you’re doing, even WORSE is to have built an entire career around ‘faking it.’ You’re a fraud (and deep down inside you know it), but now everyone else has bought it so you have to make sure to maintain the pretense. You’re a victim of your own success. People who have their ‘faking it’ house of cards threatened can be incredibly hostile — because after all, there’s nothing else to fall back on. Conversely, there is nothing quite so liberating as being authentic about who you are and what you know (or don’t). Outing yourself and realizing that the sky doesn’t fall down on top of you can be incredibly freeing. It actually frees you up to learn from people.
The second danger is more nefarious — people who have embraced positive thinking and posture and language to the point that they’ve internalized ‘faking it’ and no longer know the difference. These people are incredibly dangerous, and uniquely American. If I’m going under the knife, I want the cantankerous old doctor who checks all the traps, not the fresh young resident with a positive attitude and a projected confidence to fill in for experience. (This is made even worse by managers who promote people based on positivity or confidence rather than demonstrated talent or skills.)
I’m *not* saying that there’s anything wrong with projecting confidence — only that it’s a tactic, not a strategy. Rather than “vanquishing” your insecurities, use them as motivators to learn what you need to learn.