We are often taught to believe that we should ‘know everything’ and act accordingly. A majority of folks are hesitant to show that they may not know something or may not know how to do something. We have society and our egos to thank for that. Here is the thing though, that is an amazingly unproductive line of thought.
If the choice is between being expert at what you do or knowing a little about a lot, go with the being expert. Experts are worth more, and have a better rate of success. Knowing a little about a lot puts you among the masses. You are just more white noise.
Of course to be an expert in your field requires continuous education, specific relationship building, etc. You can’t just rest on past knowledge and performance. Like Denis Waitley says, “Never become so much of an expert that you stop gaining expertise. View life as a continuous learning experience.” So if you aren’t willing to invest the time, don’t bother going down the path.