I learned the principles of cybersecurity from mystery writer John Dickson Carr AKA Carter Dickson. Among his many talents, John Dickson Carr is the master of the "Locked Room Mystery", in which a man or woman is found dead in a room locked from the inside -- a clear case of suicide. However, it's never suicide: it's always a fiendishly clever murder.
The lesson of the Locked Room Mystery is that no room is sealed if there is an opening, no matter how small. Here's how it applies to cybersecurity: if there's a connection to the outside world, there's a way in and it's just a question of time before it's breached.
My company provides mandatory cyber-security training for all employees. Each year we receive refresher courses. The training covers technical as well as social aspects of the risks. While I am bound by company policy from discussing exact details, I found the training informative and useful.