This Mark Twain quote has wisdom to it. It points at the idea of knowing where your knowledge stops, if you don’t know this your arrogance might get you into trouble. Martial arts movies are full of scenes where someone goes into a dojo, thinking they are well-hard and challenges the instructor. I have heard personal anecdotes of a similar nature in that world. Someone who makes a living in martial arts probably knows their onions, so such behaviour is a bit silly. The person making the challenge may not be aware of the limitations of their knowledge but with testicles full of spunk, they imagine they do. It is best to approach the unknown wide awake and with humility.
Many people do really stupid things like playing with Ouija boards and then are a little surprised when they very quickly get out of their depth and into trouble. In this case playing with fire is no so good. As a practised pyro, I am safer with a can of petrol and a box of matches than most. I have a fairly good, though imperfect understanding, of where that knowledge ends. I nearly always have water handy.
If you are to extend your knowledge, then it stands to reason, that you will have to approach the unknown. There will be some things that are unknowable, to you as a being, they are beyond your capacity. This approach is called sanity.
If you are to approach the unknown, then it stands to reason that the approaches or methods that work in the known, will probably fail. The tools may cease to be fit for purpose. The further you venture into the unknown, the more likely it is that the previously “tried and tested” will not work. Thus, to approach the unknown one needs new approaches.
If you like high adventure, then you might simply, full of bravado, jump into the unknown. One can get very lost in the unknown and each being has their own predilection, for adventure.
By definition the unknown lies beyond current understanding and knowledge. Having cued up approaching the unknown, I’ll return to it a little later.