You know what you know. Simple enough.
What you don't know you don't know is always a challenge.
In between- what you Know you don't know - is (ideally) your development plan, whatever kind of knowledge pursuit it entails.
But what is often time neglected is what you don't know you know.
It could be hiding in your data, it could have been the outcome of an meeting that was never communicated, or a lab result that simply got buried away in the gigabytes of old data nobody has a clue about….
So before worrying too much about what you don't know you don't know, see if you can leverage what you already know.