The high quality of the epic poetism involved here might make the recipient doubt about whether you are the true author or not. Therefore; It is better, to sign the work with a well chosen, personal signing-off phrase. The letter is thus attached to your personality and you can thereby claim that you possess some of the authorial qualities displayed.
Guiding principles for the writing of suitable signing-off phrases:
You own little/big teddy/kitten, John Doe