Check out The Calculus of Grit by Venkat Rao. This article is somewhat similar to my Jack of all trades post but goes into far more depth. It is about 20 times longer than my article and well worth reading.
Venkat Rao compares discipline boundaries to extrinsic coordinates and one’s career to intrinsic coordinates. You don’t have to understand the mathematical significance of these terms to read The Calculus of Grit, though it helps. Extrinsic coordinates describe a surface as it sits inside a larger space. Intrinsic coordinates describe a surface as it would be experienced by a bug crawling around on it. A line that is straight in one coordinate system will typically not be straight in the other coordinate system.
For some background on the technical use of the term “grit,” see the Psychology Today article The Winning Edge. (The math in the first paragraph is annoying because the superscripts were stripped in the online version of the article. It says, for example, 32 + 42 = 52.)
Thanks to DavidC for pointing out Venkat Rao’s post.