Laura - we had Christmas and New Years between the diagnosis (Dec 6) and the radiation planning. Ugh. The first Cetuximab infusion was January 14 - and radition on the 21st. It was a relief getting started.
I found that meditation helped me mangage better - I'm not very good at it, but my BIL's advice to do breathing exercises was a real lifeline. The other thing that helped was to concentrate on the things I had some control over - learning about the disease, learning about food and nutrition, buying skin creams, stuff like that.
Please try to find pleasure you can in the holiday session. A drive together, a favorite movie won't generate happy-go-lucky glee, but my husband and I had quietly happy times as we worked the tunnel hand in hand. You are stronger than you think.