Wedding RSVP Cancellation Message (3F Formula)

"Hey [Friend's Name], I am so incredibly sorry to be sending this message, especially so close to the big day. (Fact) An unforeseen and unavoidable personal matter has come up, which means I devastatingly won't be able to make it to the wedding after all.

(Feelings) I feel absolutely terrible about this, especially after RSVPing 'yes' and knowing how much I was looking forward to celebrating with you both. I'm truly gutted to miss it and to be causing you any additional stress right now. I can only imagine this is frustrating news.

(Freedom) Please don't feel any pressure to respond to this amidst everything else. My only thought is for you to have the most wonderful wedding day. I've already sent along your gift, and as a small token for this awful situation, I'd love to take you both out for a special celebratory dinner when you're back and settled. Wishing you so much joy."