Here's the thing about fireworks. At least wait until July 4th to see if any go off. In my neighborhood, there's regulations about when we can even light them. We have our meeting with KD on July 1st, supposedly. He's leaving for a shoe tour on July 9th and his decision is expected before then. If you're lounging on a grassy hill eating a hot dog whining about the lack of fireworks going off on June 26th, you'll look kind of silly. Let's wait until the scheduled time next month for the show and first see if Boston shoots off some duds. We aren't even there yet.
This is fair. In the case of Durant, I agree—we won't know until July 9 (or perhaps a few days sooner).
In general, however, we've already waited through "July 4th" several times—the recent draft, the last trade deadline, last summer, last year's draft, etc. I don't think Danny's made any dumb moves; in fact, he's made some pretty smart moves, albeit on a smaller scale (JJ, Amir, Crowder, IT). But, as greece666 said, the typical cycle of hype-hope-horror is already happening again with Durant.
Anyone upset with Ainge needs to clam down and be patient
We are in the process and next summer will be the true key for fireworks
I truly mean no offense, but it's statements like this one that have led to lots of Cs fans (myself included) getting our expectations up. High expectations are partly the fault of those of us who let our expectations be raised, but between Wyc's talk of fireworks and certain Cs fans saying things like "just wait until (fill in the blank—next summer/next trade deadline, etc.), it's exceedingly difficult to not hope or get excited for "what might happen."
For me, I wasn't disappointed with the Brown pick—not at first, anyway. As the night went on, though, and legit basketball reporters such as Woj were saying things like "The Celtics are in negotiations with Chicago for Jimmy Butler" (or something to that effect), and then those things didn't come to pass, and then I learned about certain picks being draft-and-stash, and other picks being traded for future picks ... well, seeing the can get kicked down the road yet again was pretty disappointing. And then I saw the disappointment others were expressing, and I let myself get sucked into it even worse, and I started thinking more about Brown, like, "Great, another player who can't shoot well." Etc.
He's growing on me, though, and I also understand more now about what the optimists are saying (though I think that some people are a little extreme in their optimism, but I digress), so I'm going to try to stay patient with all of this—but without expecting much. 
Nailed it. It has happened to me too, as my expectations for the Rondo trade had become too high based on what I was reading.
And I should say I can see this happening already. It's not like people are waiting for the next summer.
Now it is KD. How high are our chances for KD realistically? 10, maybe 15 %? And you can still find line ups based on KD coming here ('First we sign KD, this convinces Horford to come, then a couple of elite veterans etc'). It's this build up of expectations that leads to disappointment.
It's great that we have a meeting with KD, which means we have a legit chance—but what are the actual odds? 10-15%, as greece666 suggests? Maybe slightly higher, or slightly lower? So, while we have a legit chance, that chance isn't high. Yet most people around here are already salivating over the possibility of KD and Horford, making it seem like it's more likely than not.
If Boston somehow pulls off signing KD, I'll be ecstatic, and I'll also be happy to eat crow if necessary. But it seems unlikely to me. And don't get me wrong—I respect Danny for having a general plan (improving incrementally while maintaining flexibility for any big opportunities) and sticking to it. But unless and until something like that happens, it's all sound and fury signifying nothing.
