In the movies Christmas is unfailingly a happy time for everyone.
In real life a lot of people find it incredibly difficult, long standing family conflicts, some still hanging over from last year.
Some where some family members are not speaking to other family members etc. add the fuel of alcohol and we are often looking at an explosive situation.
If this is your situation I would suggest you limit your time frame, tell people in advance that you can only stay a short time, arrive late and leave early if at all possible, and remember there are millions of families out there with the same struggle.