As we age, we develop habits that become ingrained. The biggest issue I face when coaching and training people on effective non-verbal techniques is overriding these existing habits. Using a variety of methodologies I work on creating new neural pathways and building "muscle memory" for the new ways of communicating non-verbally. The hope is that once the muscle memory is created it becomes the new habit and they never have to think about it again.
*Above you acknowledge aspects non- verbal communication such as intonation or gesture. Intonation is para-verbal (tone), not non-verbal (body language.) Using your mistake as the example to your question, how often to people reflect on the communication they have used in an interaction? And if they do, what does that self-reflection look and feel like. Imagine instead how empowering it could/would be if we all heightened our awareness in all three areas we communicate (words, tone, body language) and what impact and efficiency that could lead too.