I think it's a great idea to take a break from shopping now and again. If it fits in with your lifestyle it's best to buy fresh fruit and vegetables little and often, but most of us get carried away around the supermarket now and again as we succumb to a special offer on something we don't really need or only needed one of, not six. Old fashioned list writing can help there, as can shopping in small independent shops, but not everyone has decent small independent shops near by.
However, I'm not sure how helpful it is to have National Buy Nothing Day in Britain at the end of November when many people will be trying to get their Christmas shopping done to beat the mad December rush. There are also a lot of Craft Fairs and Christmas Markets around where we could well buy something unique, or at least a bit out of the ordinary, made by a local craftsman or woman that someone we love would really appreciate as a Christmas present.
Personally I would encourage you to treat tomorrow as an encouragement to think more carefully before you buy, to consider if you really need that 'bargain', can you eat all 3 packets before the sell by date without ruining your waistline or consuming a very unbalanced diet for the next week or so? Let it be the day you think carefully whether Aunt Flo really would like that attractive item on the craft stall that when you think about it will probably just add to the clutter in her house and has no real use.
Do make a resolution to buy nothing once a month or once a week and enjoy doing something completely different, like taking a short walk in your lunch break and taking in your surroundings.
Do take a few days off from shopping after Christmas and resist the urge to treat the after Christmas sales as an entertainment. Use the extra time to play board games with the family or go for a walk or something else that enhances your life and relationships, but if it's not helpful for you to buy nothing tomorrow, don't feel guilty about it at all.
By all means spend more time enjoying the things that are free in life, and often more life-enhancing. What could you do if you spent less time shopping?