Certain professionals can't achieve 'expertise' because the work they do is random and has low validity environment.

A gambler betting at the roulette wheel  may have thousands of repeated experiences with the same event.  And for each one, they get clear feedback in the form of whether they win or lose, but you would rightfully not consider them an expert because the environment is low validity.

Similarly vast majority of stock pickers and active investment managers, do not demonstrate expert performance because stocks are a low validity environment.

Growth happens when someone presents a perspective that causes an individual to reevaluate their current position.

In particular, feedback is about helping people close the gap between where they currently are with regards to their performance, and where they need to go to achieve their goals.

If you want to keep improving you have to put yourself in challenging situations.

In order to get to an expert level, you have to be practicing at the edge of your ability, pushing beyond your comfort zone. You have to use a lot of concentration and methodically repeatedly attempt things you aren't good at.

This is where coaches and teachers can play an important role. They can recognize your weaknesses and assign tasks to address them.

Do they have extraordinarily high IQs, superior spatial reasoning compared to the average, or better short-term memories? It turns out that chess masters are not particularly exceptional on any of these measures as a whole.

Chess experts don't have better memory in general, but they have better memory specifically for chess positions that could occur in a real game.

Magnus Carlsen(Chess World Champion) recognizes chess positions the same way we recognize faces. And recognition leads directly to intuition.

This can be shown using an experiment carried out with Humans and Rats. There was a red button and a green button that can each light up. 80% of the time, the green button lights up. And 20% of the time the red button lights up, but randomly. So you can never be sure which button will light. And the task for the subject, either rat or human, is to guess beforehand which button will light up by pressing it. For the rat, if they guess right, they get a bit of food. And if they guess wrong, a mild electric shock. 

The rat quickly learns to press only the green button and accept the 80% win percentage. Humans on the other hand, usually press the green button. But once in a while, they try to predict when the red light will go on. And as a result, they guess right only 68% of the time. We have a hard time accepting average results.

To become an expert, you have to practice for thousands of hours in the uncomfortable zone, attempting the things you can't do quite yet.

At its core, expertise is recognition. And recognition comes from the incredible amount of highly structured information stored in long-term memory. To build that memory, requires four things: many repetitions, a valid environment, timely feedback, and thousands of hours of deliberate practice.