It's always gratifying when you hear from a reader how something in your novel has had an impact on them - be it funny, sad, thought-provoking etc. But the best kind of impact is to inspire someone in some way. A reader once told me how four words in a sentence one of my characters, (Kate), spoke helped her through the last semester of her university degree. Bogged down, tired and discouraged, she was on the verge of giving up but when she read the words "sheer force of will", it gave her the focus and determination to just push through with her own studies and finish what she'd started, even though she wasn't sure it was even what she wanted to do anymore.