How to write a letter of continued interest?

First, I'm sorry you've been deferred. I know it can seem like the end of the world but I promise you, it isn't. Back when I was applying to colleges I was originally waitlisted to my top choice which bummed me out a lot. I ended up not getting accepted to that school and I was crushed. I was determined to get accepted and applied to transfer after my first semester. Due to a clerical error they never got parts of my application so I was turned down again. In the end I'm incredibly thankful the transfer app was never sent and it ended up being one of the best things to happen to me. I'm glad that you seem determined to do whatever you can to help improve your chances of being accepted but know that even if it doesn't work out for this school things will work out. Collegevine has a few blog posts about letters of continued interest you might find helpful. There's this one, https://blog.collegevine.com/deferred-or-waitlisted-tips-for-writing-a-letter-of-continued-interest/, and also this one, https://blog.collegevine.com/how-to-get-off-the-waitlist/.

If you email support@collegevine.com I can also give you a PDF I have that has some more info on LOCIs although I think pretty much everything in the PDF is covered in the blog posts, especially the first one.