The mistake I made when I was younger was thinking that good communication was about being able to clearly and concisely convey the information in your head into another head.
I eventually learned that this was necessary but not sufficient, because "the right way" to communicate varies significantly based on social / political / cultural / emotional / institutional dynamics.
As a young man I simply didn't understand enough of those dynamics to be able to model the when and the why of communication (meta-communication?), even if I was good at the idea transmission part.
Life experience helps immensely here.