An interesting question!
I go through this each and every trip with the worrying. Yet somehow it always lives up to billing.
I think the average person frequenting these boards, no arrogance intended (don't know what it would get me anyway!), is to some degree a Disney pro. We all know how to work the system and squeeze a dollar ten out of every buck we spend.
For myself, going in June and then again in the low-season in the fall, I fret my June trip every year. Yet it never fails to live up to and past expectations. I've finally settled into a groove. I believe I have a leg up on the average Disney traveler in several ways:
I know to either not go on Easter, July 4th, Xmas, etc, or else to accept what I'm going to find there.
I know when I go in the fall, things will be closed, and when I go in June, everything will be open but more crowded. I make up for this by keeping in mind that there is SO much to do and I'm getting to the point where with a little research to see what's changed in the last couple months, I can be where "they" aren't.
I've been to Disney over 30 times in my adult life. I know there is a ton of stuff to do, and I've seen everything enough that if I have to miss something today in order to miss a crowd or duck a shower, I know I'll catch it tomorrow. And if I miss it this trip, I'll catch it in the fall.
After living through seasonal downpours, hurricane warnings, and the dreaded squalls while in MK on a Saturday, I know not to fear the rain. If it rains, I get rain gear on and do what I do. And if it rains really hard, I get wet. So what? When it's not raining, it's really, really hot, and I usually have to head back to the hotel. To jump in the pool. To get wet. Go figure.
In short, I began to realize that WDW isn't Epcot, or MK, or The Boardwalk, or DTD, or even the Adventurer's Club (ok, maybe it IS the AC). It's a feeling I get when I'm surrounded by it. I'm as happy sitting under cover in front of DTD's World of Disney, waiting for the inevitable 4 PM deluge to stop as I am riding Spaceship Earth. I'm addicted to Disney and I'm just getting my bi-yearly fix. And it doesn't hurt anyone but my accountant.
That said, if DIS begins offering recreational therapy, I'll take it...