Researchers David Dunning and Justin Kruger, conducting an experiment in 1999, observed a phenomenon that’s come to be known as the Dunning-Kruger effect:
Unskilled persons tend to mistakenly assess their own abilities as being much more competent than they actually are.
What follows from this is a cognitive bias in which people who aren’t very good at their job think they are good at it, but aren’t skilled enough to recognize that they aren’t.
Illusory superiority has been found in individuals’ comparisons of themselves with others in a wide variety of different aspects of life, including performance in academic circumstances (such as class performance, exams and overall intelligence), in working environments (for example in job performance), and in social settings (for example in estimating one’s popularity, or the extent to which one possesses desirable personality traits, such as honesty or confidence), as well as everyday abilities requiring particular skill. Illusory superiority is often referred to as the above average effect. It is one of many positive illusions relating to the self, and is a phenomenon studied in social psychology.
You’ll notice that Dunning-Kruger effect don’t directly apply specifically to software or development. The fact remains that software is built for people to use and interact with, so in proccess of software development you have to work with other people to create software so it’s good to know this law and be aware of it.
No pithy quote will ever replace the experience you gain every day by writing code, interacting with users, and generally practicing every day. Still, by keeping in mind this law, you might just make yourself a better developer.