One way I can try is this: have you ever experienced the difference between "I know what I'm going to say, and here I am saying it" and "words are coming out of my mouth, and I'm kind of surprised by what I'm hearing myself say"?

BTW, my internal monologue usually sounds quite different from what I actually say in most casual situations: for example, it uses less dialectal/non-standard language and more technical terms. (IOW, it resembles the way I write more than the way I speak. So, "I know what I'm going to say, and here I am saying it" is my default state when writing, and "words are coming out of my mouth, and I'm kind of surprised by what I'm hearing myself say" is the state I'm most often in when speaking.) Anyone else finds the same?