Simply replace the unfilled areas such as "__" and "_[date]_" with your information.
Dear [name of spouse]
I love you so much, and a thank God everyday that he gave me such a wonderful and special wife. You are everything that a good, Christian woman should be. You are kind, charitable, and loving. You are strong of heart and are always there to listen and provide an honest opinion when I need it. You are the best mother to our children, and I know that you would do anything to provide them with the best possible upbringing. Just in case I don't say it often enough: Thank you for choosing to marry me, thank you for continuing to put up with me, and I love you so very much.