I long ago read an article on the inchworm theory, which is a gaussian curve rappresenting performance with frequency on the x axis and performance on the y axis.
Avarage performance occurs most often, sometimes we choke and some others we are flawless. Therefore improving our best possible performance by learning new things is not sufficient: in the same way an inchworm pulls his back part of the body forward, we have to improve our worst possible performance to improve.
This theory can be further expanded by realizing the power of inversion and how problems are often times asymmetric.
For instance it may be easier to find ways to spend less money rather than make more of it.