I think the pressure he may feel now is different. HBO won't pressure him a bit to finish the series but he also has to know that if he doesn't they will effectively do it for him. They own the rights to the show and they can take it however they like. In truth, if he didn't finish it gives them even greater freedom and more interest. Every season that passes will involve more shifts from where GRRM wants to take the books. If he wants the story to be his then he must make it so, regardless of the fact no one could actually write the end to the books (which seems odd as well btw).
I would think he wants to get it done so he can move on to truly enjoy the rest of his life.
I would think he wants to get it done so he can move on to truly enjoy the rest of his life.