It's ok to be a couch potato for one day. As a matter of fact it is good to do it. It feels good to not go outside one day and instead cuddle up inside with a good book or just catch up with your favorite TV shows and do absolutely nothing. Order take-out, better yet: delivery.
It's ok to go back and rewrite one or two of your new-year resolutions. More realistic and approachable goals will make you happier and most importantly you get more results when you focus on the day by day action when compared to a deadline.