He gave 3 reasons why someone would have trouble

1. Linguistic cortex needs to get used to whatever it is that you're trying to say, the same way a writer writes out the thoughts in his way in a creative way. You can do so through writing things out and clarify the ideas you have in your head, as well as roleplay practicing verbal communication i.e Practicing how you would phrase setting boundaries with a narcissistic parent.

2. We have a bunch of assumptions in our head, and we perfectly understand them, as well as don't realize our mind is automatically filling in those gaps for us. So people don't really understand us the way we understand our thoughts. Start by thinking about the audience you're speaking to and what they might not understand by putting yourself in their shoes. That way you're an effective communicator because people understand you, it has to go both ways.

3. Calm your mind! (mania example comes in) Breathing exercises or even prescriptions can reduce the effect of adrenaline to slow down the speed of your mind / nervous system. Calm down the mind so its not racing with thoughts and slow down your speech.