Kim Kardashian writes her kids letters every year on their birthday so they remember their childhoods

• Kim Kardashian spoke about parenting on the "On Purpose" podcast.
• She said she writes four-to-five-page letters for each of her four kids on their birthdays each year.

Kim Kardashian said she writes each of her four kids a four-to-five-page letter on their birthday about the year they've had.

Kardashian has four kids with her ex-husband, Ye — the artist formally known as Kanye West: North, 9, Saint, 7, Chicago, 5, and Psalm, 4.

In an episode of the "On Purpose" podcast released on Monday, the 42-year-old reality TV star told host Jay Shetty: "It's so fun to see from the first year, now one of them is almost 10 years old."

Kardashian said the letter includes who their friends are, "silly words" they're saying, their favorite foods, and the "silly things " they do.

"I know that they'll appreciate this," she said, adding that they'll even appreciate the times when they thought she was being harsh or over-protective as a parent.

She said she knows that they'll understand when they grow up, because as she got older she "got it" with her mom, Kris Jenner.

She also went into detail about the struggles of being a single parent and "mom guilt" on the podcast.