"Practice the 80/20 rule - The first twenty percent of our time and effort often produce eighty percent of the benefit from a given outcome; the remaining eighty percent of our effort only yields an additional twenty percent of the benefit."
Now how could they possibly know that! Sounds suspiciously like a plagiarism of Pareto's famous observation but without the genius.
"Overthinking is also often associated with mental health issues like depression, anxiety, post-traumatic stress and borderline personality disorder."
The real problem is overthinking underthinkers, that is, underthinkers who overthink, such as they are capable.