If you are a professional software developer, or aspire to be one, you will need to know a lot of of things. Various maths, stats, languages, frameworks, methodologies, tools, etc. Fads and buzzwords will come and go, all during your career. You’ll master some, ignore some, laugh at some.
But aside from the desire and ability to work in abstracts for concrete results, there is one skill that is an absolute must-have.