You become an expert by leveling up in knowledge, let's take a poker game for example:

   0: learn the rules
   1: what do I have
   2: what might the others have
   3: what might the others think I have
   4: what might the others think that I think they have...

You have to evolve through each level step by step, and develop an intuition before you can go to the next level... There are different levels of abstractions in thinking, and experts tend to have been at all levels. To have the best odds of winning, you need to determine the level of your opponent, and pay exactly one level higher.

You can find more info on a similar school of thought by googling for "dreyfus levels of skill acquisition", which explains the 5 levels you have to go through to master something:

   0: What are the rules
   1: I know the rules
   2: I understand how the rules work
   3: I understand how the rules work together
   4: I see patterns and develop an instinct
   5: I understand why the rules are there, and would know when to deviate

If your mind is no longer preoccupied with thinking about the rules, you can start doing other things with your brain, which is why practice is so important.

I actually had a talk a decade ago about this: https://www.slideshare.net/mobile/TomJanssens1/getting-bette...

Edit: updated my last poker rule; it has been a while, and I am typing this on my mobile..