After recently reading about the "Ten Thousand Hours" rule from Malcom Gladwell's Outliers, I was left thinking. The rule states that it takes roughly ten thousand hours of practice to achieve mastery in a field.
UPDATE [Nov 2016]: I think the original research, more worth reading is Anders Ericsson's work and his latest book Peak. I wish this book had come out earlier than Outliers.
These books made me evaluate everything I've done in the past six years as a software developer. Looking at the ever changing landscape, I don't think reaching mastery is a feasible goal. Rather, acquiring the mindset to grasp fundamentals and leverage the best tool for the need of the hour seems like a more sensible approach.
There are two extremes when judging your capabilities. Assuming that you do not know anything (Imposter syndrome) vs assuming that you know everything (Dunning-Kruger effect).
In short, the Dunning-Kruger Effect is the name of a cognitive bias where people consistently rate themselves as being higher skilled than others. Diametrically opposed, is the Impostor Syndrome, where people refuse to acknowledge their accomplishments and competencies.
I guess knowing what you do not know is a good place to be.