In the book, it was said that before the wedding Daisy received a letter from Gatsby. I think it was written the following:

                  My dear Daisy,
         
             I'm sory I didn't write you so long. I have some problems, but I always remember you.
             You're the most beautiful girl in the world. I want to be with you. Unfortunately, the situation is that we have not seen. But I will do everything possible to be more close to you. Do not forget me. You're wonderful. I love you very much.

              I hope to see you soon.

             With love,
             Yours Jay