1. Your clothes will be perpetually wrinkled. It never fails that you have a load of laundry in the washer and/or the dryer when people want to come through your house. So they sit in the washer/dryer for a very long time waiting for you to be allowed back into your own home. And if you are lucky enough to get them folded before you leave, note that you will definitely not have time to put them away so they will live in their laundry basket in your car for days at a time after the showing(s).
2. People only want to see your house after your vacuum cleaner has self-destructed and caused a noxious burning smell to permeate everything in the house: walls, carpet, clothes, etc. If the vacuum doesn't die, something else will smell hideous just to make sure this rule isn't skipped.
3. You will get fat while trying to sell your house. Corollary to that, the people at McDonald's, Burger King, and Wendy's (add in any local fast food chains as well) will be able to put your order in for you before you even reach the counter. Try not to blush when they greet you like Norm was greeted on Cheers as the other dine-in guests will surely stare at your sorry (and fat) self.
4. You will happily defect to the parenting dark side (all credit for this statement of truth goes to Aimee, incidentally). You will encourage your children to forsake toys and books, which can make messes and be left out, for tv, which only has to be switched off at the moment's notice you've been given for your showing. yes, that's right: you no longer feed them nutritious food *and* you park them in front of the tv for all their waking hours. They get as fat as you do when your house is on the market.
5. It is officially illegal in several states (at least all those I've lived in) to sell your house before you are caught naked by at least one realtor and potential buyers. My theory on this is that the frightening sight of me naked makes it simply impossible for them to scrub the memory of my house from their brains. Now that we've gotten that requirement out of the way for this house, here's hoping it sells.
6. You will inevitably forget where you buried St. Joseph so that on the off chance he actually intercedes on your behalf you will not be able to follow through and dig him up to put in pride of place in your new home, leading to incredibly bad ju-ju when you go to sell that one (I mean, just how many times will a guy forgive you for leaving him buried upside down and 3 inches down? Looking on the positive side, you are contributing to some interesting archeological studies 500 years from now. Wonder just what cock-a-mamie excuse archeologists digging up all these Josephs will concoct to explain the veritable crop of small upside down saints in front and back yeard across America?
7. When your husband returns home for a weekend (once a month if you are lucky) he will make the biggest messes of all because he a) lives like a bachelor now and who cares that his apartment looks like a pig pit or has ants and b) he has forgotten that children, even those who try (and ours often don't fall into this category), are naturally crumb and spill producing. If you're lucky, he'll actually wipe up all crumbs instead of just sweeping them onto the floor but don't hold your breath.
8. Not that there is ever a good time for a pet accident, your pet will up the accident problem if the house is on the market. If you luck out, the dog will vomit *after* that day's showing, giving your clean-up efforts at least 12 hours to dry before the next showing. *Note that this does not mean the area will be dry but at least it won't squish when potential buyers step there. And corollary to #7, be prepared to find poop in little used corners of the basement because that bachelor husband of yours will forget that the dog requires walking and not do it for any of the hours you are off shuttling kids to their activities (and heaven forbid the dog stay crated while the unreliable adult is the only one at home).
These are just some of my recent observations but they seem to hold pretty true move to move. Now if everyone crosses their fingers, maybe this house will sell and I can stop worrying about all of the above (and I will make a concerted effort to find this Joseph since I'm sure we're already over our quota of abandoned saints).