These days, it doesn't take much to trigger anxiety for me, alas. No worries.
You are correct, it's not always about a planned end (and some of the best moments in D&D can come from not having one). Rather, perhaps it's about intentions. As a DM I can plan that there's a cultist that wants to summon a demon lord into the world, unleashing all sorts of horrible consequences. Their success may not be assured, but they have a goal that the party can affect, one that exists outside of the PCs. If an improved game comes up with this cultist and they didn't exist until just then and there, are the PC's subsequent actions really affecting the world? Yes, the course of events from their actions will have an effect on the world, but if they hadn't encountered that cultist, nothing would've happened, because they didn't exist. Whereas a party that knew that the cultist was out there and decided to do something else would end up with a definite consequence of that inaction.