I'm thinking of canceling my plus one 11 days before the wedding
Is there a reason you want to cancel your plus one?
Yes, I want to go on holiday earlier than schedule so I can watch the sunset alone.
Having to do a last minute change is always difficult, but weddings are typically made months or years in advance so cancelling with only 11 days left will make them very mad at you. They might never want you in their lives again if you choose vacation over their wedding.
I'm going to go on holiday, I don't care what other people think of me.
Even if you don't care what others think about you, it could still cause problems for you if they don't think they can trust you to keep your word. Since you are eager to spend some time on holiday alone, perhaps you could just meet up with your plus-one in time for the wedding, and spend the rest of the holiday by yourself.