AKA In-Field Experience
Quick Definition: The real world, as opposed to idle fantasies and online pickup forums.
When it comes to mastering the pickup arts and social dynamics, there is no substitute for the experience gained while practicing out in the field. Like many skills, pickup must be learned through repeated practice and calibration, rather than by simply reading about it in a book.
Naturals tend to have a lot of girlfriends and field experience, while keyboard jockeys do a lot of reading with very little field experience. Generally speaking, a person can become a good PUA with lots of field practice and some reading guidance, while a lot of reading with little field work will never make a great PUA. The PUG Mystery, for example, spent 10 years consistently practicing in the field before inventing the Mystery Method.