How do I decline an invitation to my Aunt's Birthday party?

Dear Aunt Ruth,

I was so excited when I received the invitation to your birthday party next Saturday.  Celebrating you and your birthday is so important to me.  You have always been one of those people in my life that has cheered me on.  I've always know I have an ally in my corner with you in my life.

My excitement turned to sadness when I tried to find a replacement at work for next Saturday.  No one was able to cover for me.  I will have to miss being with you physically.  Count on me joining you with my heart!  I will be wishing you an awesome birthday and hoping for a year full of happiness and joy.

I love you Aunt Ruth.  Thank you for the invitation.  Please don't forget to invite me next year!  I can wait for the next time we see each other.

Love,
Your Nephew