Nowadays it is not possible for someone to know everything even on a small subject. For instance lets look at Agriculture.There are highly intelligent people who spend the whole of their lives studing and working on how to cross breed plants e t c. Even though these highly intelligent and committed professionals spend their whole time specializing in a particular aspect of plant, they never learn everything finish,they still continue on research thats why we called them researcher.
Anytime am arguing with my friends i ask them a question that (Is there anyone who know it all) they will all say No. People who know it all are also called braggart or wiseacre.
A braggart is someone who is found of boasting or bragging, someone who so much believe in himself. How can you know u are a braggart? It is easy. You have stopped learning and growing in your area of specialization.
Maybe you have stop reading,learning,aslo going for courses,if you feel you know it all and you stop learning people under you will surely pass you.
If you dont seek out new knowledge in your field regularly means that you have carelessly, heedlessly, felled into the intelligence trap of the low performer.