Experts...

...are those that can do it live.

You can only be good at something if you can do it with out thinking about it.

You should only do something live if you can do it without thinking about it.

Experts are those who can do it well... live.

How do you become an expert? By doing it and messing up. Sometimes you do it live and mess up, sometimes you mess up in preparation, but either way you will mess up. Whether you should learn while live or while in prep depends on the consequences and is really a topic to be further explored.