Second: make it as easy as possible to sleep. Sleep is very important to happiness. I was afraid kids would wake up scared in the middle of the night. So, instead of people sleeping alone, people slept with a partner. Four people, two beds, almost everyone slept well through the night (let's be honest - parents with a kid in bed don't actually sleep great when the kid's feet are in their backs).
Third: Drink water! Don't get dehydrated!
Fourth: Improvise! Don't have a cup to wash your little kids with? Cut the top off the 1-liter water bottle that you just finished off and use that instead.
Fifth: Bring a Lucy! Everyone should bring a Lucy (my amazing and wonderful helper from the Philippines who moved here with us) with them. Her presence has been very important to my happiness today.
Sixth: Take a deep breath when you see the first grocery bill. And remember - you are stocking your new home with essentials that you won't be buying every time. This obscenely high grocery bill isn't going to be the norm. And also remember to fill out the COLA survey the next time it goes out because holy crap are things pricey here!
Seventh: Remember the good. Every time you have a negative thought about your new place (this house is a lot smaller than my last one, I have no storage here, my list of requests for GSO is getting kind of long), try to remember the good about the house (I have four bedrooms for the first time in my life, the master suite is huge and I have a soaking Jacuzzi tub in it).
And finally - finish the first day off with a bath. A really nice bath in your really nice Jacuzzi tub.
Because you've just survived the first 24 hours at post without crying. For the first time. And that is definitely worth celebrating.