For me, it's when something I've written makes a connection with a reader. I love it when a reader describes how a scene in one of my books led to an emotional response, or how the premise of one of my stories reminded them of something they've been through. It can even be as simple as seeing someone in the crowd at a reading laugh or nod their head or lean forward for more. Frankly, any kind of connection with readers - in-person or written - is special, and what I think of as success.
I don't tend to put actual events I've lived through in my books (I prefer to imagine!). However, I do draw quite a bit on what I think of as my "emotional memory". Especially when writing for a middle grade audience, I try to keep in touch with how my "middle grade self" felt about things and perceived the world at that age. When I can connect emotion to whatever obstacles and scenarios my characters are going through, that's when I believe I write with most authenticity.
Having my first book published was such an exciting and amazing opportunity in so many ways, including for my growth as a writer. For one thing, it led me to go further studying the writer's craft and to figure out for myself the best balance between the planning stage and getting going on my drafts. It also opened up the opportunity to teach creative writing workshops. Fast forward years later, and it means I've had the chance to meet and work with thousands of workshop participants. The inspiration that I myself have received from working among all this creative energy has been immeasurable - and that would not have happened had it not been for my first book!
Books are a part of my earliest memories as a child. I've kept a number of the picture books that I remember my mom reading to me before bed at night and they have a special place on my shelf. But when Mom read "The Lion, The Witch and the Wardrobe" by C.S. Lewis, offering a chapter a night (maybe slightly more if I insisted!) - that's when I knew I wanted to write "chapter books" one day, too. As I recall, it also kickstarted my determination to learn to read independently (so that I could read two or three chapters at a time whenever I felt like it!).
