Let's admit the holidays can be tense & there can be strains in our relationships with family. My sister & I notoriously bickered & argued & my mom would beg us to not bicker on the holidays or her birthday. She'd ask for one peaceful day. We tried but weren't always successful especially when we were younger. Thankfully we get along now but when we were young, it was a bit different.
I understand I am giving a simple example but even in the simplest of circumstances the holidays can be challenging. You could be hosting 20-30 people, family may choose to go to someone else's home or spouses &/or partners don't like each other. Either way, I think it is important to prepare for the challenging moments.
I think some things that are important to remember is to prepare yourself, try to set realistic expectations about the day, if you need to prepare your kids, do something kind for yourself (i.e. take a moment to have a cup of coffee or tea by yourself, have a bubble bath, etc), choose not to engage in the tension when possible. There are a lot of things we can do for ourselves to prepare for potentially awkward & tense days.
I have included some articles below with some good suggestions for managing tense relationships during the holidays.