[Eric C]

This is sometimes called "interior monologue" and you can read up on it in a lot of self-help fiction writing books. Or you could crack open your favorite novels and see how it's done in them.

The italics are optional. If you do it well enough the italics aren't needed, and the "he said to himself" aren't needed.

 

[Eric C]

Here are some interior monologue tips from "Self-Editing for Fiction Writers" by Renni Browne:

Maybe the most useful how-to book for new fiction writers ever written. (But there was a coauthor, Dave King.)