Are you avoiding a task (for example: calling on a particular group of prospects, writing an article for a trade publication, or giving a speech to an organization) simply because you didn't consider yourself an expert in the particular endeavor? Perhaps, the perceived complexity of the learning process or amount of time it would take to become an "expert" has discouraged you from making any attempt.
Do you have to be an expert?
Are you an expert driver capable of taking a Formula 1 car around a 14-turn Grand Prix track at 200+mph (without damaging the car...or yourself)? Probably not. But, I'll bet you can competently drive your car, day to day, to get where you need to go.
Are you an expert chef capable of whipping up a gourmet meal for 14 guests with only three hours notice? Again, I suspect not. However, I'll bet that you can toss a salad, broil a few steaks, bake a few potatoes, and steam some vegetables competently enough to even please your in-laws. (OK, that may be stretching it...but you get the point.)
The same applies to speech making, article writing, and prospecting. You don't have to be an expert; you only have to be competent-in many cases, only somewhat competent.
But, you'll never become competent without first "giving it a try." If you've been putting off writing that article or outlining that speech or developing that compelling prospecting strategy, stop procrastinating and just start. Ask a friend or colleague to review your work and make suggestions. With a little effort...and faith, it will come together.
No one starts out as an expert; they must first develop competency. And, no one develops competency without first starting out. So, what are you waiting for?