Yes you are right, someone who feels smart and feels that their knowledge is already abundant, they will likely close themselves off from something new, that is what ultimately makes them lag behind because they never want to upgrade their knowledge.
If there is a person who feel this, he will never be a true smart trader. He will never be a professional trader as well. There is no professional trader that feels having everything and knows everything. He must always keep learning because he knows that he must improve their knowledge to achieve higher target. The person who doesn't upgrade their knowledge, will never be smarter because his knowledge never grows.
This is a wrong mindset, which they will feel a loss in the future, not a loss in terms of finance, but a loss because they are left behind from new knowledge.
Indeed, it is wrong way. If he knows how to be a real trader, he won't feel in that way.
When we are being arrogant because we assume to be smart one, it is the beginning of no progress of advanced learning.