There is a stark difference between knowing something well, and being confident in it. You can be knowledgeable about investing. But without confidence, you won't be able to put that knowledge to the test, and you won't be able to gain from that knowledge. You can be knowledgable about language. But without confidence, you won't be able to make use of that knowledge and use the language for the reason it is there, to be used as a tool for communication.

Knowledge is only ever useful if you have the confidence to use it. Otherwise it's just knowledge.

Full disclosure: This blog post was heavily inspired by a conversation with my colleague Mirzosaid Sultonov.