I think the best advice is to not "coulda woulda shoulda" after the fact (or anticipate it during your trip).
By that I mean, let's say some catastrophic event happens (Brer Bear finally falls out of that hole in Splash Mountain) and that ride is closed while you are there. Instead of letting it get to you, just think of it as something to look forward to on your next trip (even if it's many years away).
You will not see EVERYTHING. If you concentrate on the parks, you can see MOST of everything in a week, but there is always going to be something you'll miss. Accept this, and embrace it, before you go. Go over it with the kids - let them know you are going to have a great time no matter what, and if you do miss something, don't be one of those parents (if you are bringing kids) that says missing one thing "ruined the whole trip" (it's amazing how many times you will hear people cussing out CM's and saying that).
Just focusing on seeing as much as you can, but don't build up expectations in case everything doesn't work out exactly how you planned it. The key to planning a Disney trip is to do as much planning beforehand so you can plan on the go, not so you can stick to a minute-by-minute schedule you made months before.
A good example of this philosophy is how I tell people about the Wishes! fireworks. Generally, Tinkerbell flies. But sometimes (as often as a couple of times a week) the weather isn't just right, so she can't fly. If you spend all day building up "hey kids, we're gonna see Tink fly tonight!" and she doesn't, you just might miss out on the magical spectacle of the show that is happening. So when I bring guests, I don't tell them - I let it be a surprise. And if it doesn't happen, they are none the wiser and still enjoy the show.
Just go and have a good time!
NED
(we'll see if I can do it).
