We do several things. I order things online after the kids are in bed. If I think they might see the package, I have it sent to my DH's job. I use one day to get most of my shopping done. I also buy gift cards for teachers (they would rather use the money). I know it's not the most thoughtful gift, but I make my DS make a really cute card. Then it becomes more personal.
I make DH help me wrap. This way he sees what Santa has brought. Anything that takes a lot of time to put together, will be put together a week before and carefully hidden.
DH and I always do Christmas (my family always visits and my Aunt has a small apartment). Sometimes we get the bonus of having to do all three holidays. Thanksgiving we also do every year, we have the space. We rotate Christmas eve with his family so every three years we end up doing all three holidays - talk about stress

So we decide on a menu early and decide what can be made and prepared ahead of time. I premake a lot of things like soups, pies, appetizers, etc. We also do more roasting like roasting veggies and potatoes as it is easier to throw it in the oven. I also then refuse to cook the day before each meal and the day after. Leftovers or we order. It use to be fend-for-yourself but that would allow my DS to eat candy for dinner.
One thing I used to do, but since I haven't gone back to work yet, was hire a cleaning service to come in and do their thing. I would have them come do it all including windows. They would come two or three days before the holidays. I made my appt. early like right after Thanksgiving. It's worth every penny. I don't use a service any other time of the year and I figure it's a gift to myself and sanity. Why should I do all this shopping, cleaning, my usual work, just to spend my little spare time to clean.
For Christmas cards - I know this may sound tacky, but if you haven't sent a card for two years in a row, you get cut out. There are only a few exceptions and that is with our elderly relatives. I know it's not going with the season, but it does get expensive and I do my best to keep costs down.
Finally, I take a bath when I can. Very relaxing especially with wine. I still get a little stress and I think that is ok, a little stress never hurts.
I am always looking for other ways to calm down.
