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 recently 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 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.
This reader could already relate to Kate as they were both students and both struggling to complete their respective degrees (although my character Kate was just at the start of hers). I have often used the words "sheer force of will" to remind myself not to give up when the going gets tough. I used them many times myself throughout school and university and definitely when writing The Beach House. Yes, there were many times in all three situations when I wanted to just give up, pack it in and try something easier. But I also knew that the obstacle in front of my was temporary and if I just focused my energy hard enough I could conquer it and get the reward of what I wanted, rather than looking back in regret later because I'd given up too easily and too early.