Keep It Real - To help reduce stress, set realistic expectations (and then be willing to let even those go) or even set your expectations a little bit low to start with. Have you ever gone to see a movie that everyone was raving about and then thought, well that was alright, but not worth all the fuss. Sometimes I think that happens because you’ve heard amazing stuff about it and built it up in your mind so much that it couldn’t possibly live up to the hype. If you build up the most fantastic, amazing day in your mind, it can’t possibly live up. Keep in mind that things won't be perfect; just relax and have fun.
You are Not Martha Stewart - accept this fact and move on. That right there will get rid of a lot of stress and pressure.
Reconsider Tradition - Don’t feel like you have to follow everyone else's ideas for the Holiday. Two kinds of gravy, three kinds of cranberries, and three different kinds of pie is enough to stress anyone out! If you want to start a new tradition or be completely un-traditional, you might want to try it. You probably want to let everyone know in advance on this one especially if you have a conservative family. And hey, it might get you off the hook of ever having to host a family dinner ever again, lol
Be Prepared - Get ready whatever you can ahead of time - clean rooms a day or so in advance (and banish the kids from those rooms), fix desserts salads breads and sides ahead of time. The less you have to worry about, the more you can relax and spend time with your family and friends.
Be Willing to Ask for and/or Accept Help - Have friends and family bring a dish to share and/or games to play - This can make things easier when it isn’t all up to you to provide all the meal and all the entertainment. This makes it as easier on you, and most people really like to help and participate.
Just Roll With It - If turkey takes longer to cook than you thought, your brother arrives late, or the rolls burned, just roll with it - don’t let little things ruin your day, just go with it, keep a sense of humor, and make the best of things.
Keep in mind that the meal does not define you. Your family and friends will love you ( or hate you :-) ) regardless of the meal. You do not have to plan, cook, serve, and clean up perfectly and without any help. Don’t try so hard to impress anyone, just enjoy yourself and keep in mind the things you are thankful for.
Happy Holidays! . . . and good luck ;-)