For Miles, one of the great mysteries of marriage was that you had to actually say things before you realized they were wrong. Because he'd been saying the wrong thing to Janine for so many years, he'd grown wary, testing most of his observations in the arena of his imagination before saying them out loud, but even then he was often wrong. Of course, the other possibility was that there was no right thing to say, that the choice wasn't between right and wrong but between wrong, more wrong, and as wrong as you can get. Wrong, all of it, to one degree or another, by definition, or by virtue of the fact that Miles himself was the one saying it.
Miles finds marriage perplexing, especially the notion that he often doesn't realize the inappropriateness of his words until after he has spoken them. His long history of miscommunication with Janine leads him to be cautious, frequently deliberating in his mind before verbalizing his thoughts. Despite his attempts to filter his observations, he often misjudges the situation, realizing that even his best intentions might miss the mark.
This contemplation gives rise to a broader reflection on communication in relationships, suggesting that sometimes there may not be a clear "right" thing to say. Instead, the reality could be that all options are flawed to some degree, indicating that, in Miles' experience, the dilemma is not simply choosing the correct response but navigating through a spectrum of errors in expression. His self-doubt further complicates his interactions, making him question the very nature of his words.