Reading children's books can help explain the abstract concepts of grit and growth mindset to young students. I love the book Whistle for Willie (1998) by Keats and have shared it with hundreds of children to teach perseverance. A new book on my shelf Nadia: The Girl Who Couldn't Sit Still (2016) by Gray is a example of how biographies are a great genre to teach these concepts. Another great biography is Salt in His Shoes by Michael Jordan's mom and sister.
There are several good lessons online that use The Most Magnificent Thing to teach goal setting, grit, and/or growth mindset including MostMagnificentThingTeachingGuide and https://twowritingteachers/spires/ The latter has a very good anchor chart similar to the one I develop when teaching growth mindset in grade 2 and 3.
Here are others I use in grades K-3 in either tier 1 class lessons or tier 2 small groups:
Giraffes Can't Dance by Andreae & Parker-Rees
Flight School by Judge
You Can Do It Bert! by Konnecke
What Do You Do with an Idea? by Yamada
The Dot by Reynolds
Ish by Reynolds
Extra Yarn by Barnett
Making A Splash: A Growth Mindset Children's Book by Reiley
Everyone Can Learn to Ride a Bicycle by Raschka