How do you retell the idea in your own words?

That's a big struggle for me. When I was learning about Zettelkasten, the idea of immediatly writing in your own words the summary of a chapter feels daunting. What if I use the wrong words and wouldn't understand later? What I want is to have notes from the book and then use them to write summary maybe in a week after reading a chapter. I can't just do it immediately. What do you think are some good ways to aproach telling in your own words?