The Holidays are always tough- this is what I have done that has helped me:
1. avoid looking at old family photos with the person in them
2. avoid songs like "Blue Christmas" and any others where you can feel yourself starting to get pulled into a slump
3. try to remember the Holidays you had when you were a child and BEFORE your ex was in the mix
You can get through it, and it will get easier over time. Have you met someone new?