I've been running games for about a decade now. For the longest time, after a session players would ask me things like "What was down that other path?" or "What if we had done X?" And I would answer them, because I had all this cool stuff I had ready for them to discover and I wanted them to know about it. They would go "Oh, hey, cool," and I would feel happy because my prep wasn't wasted.

But eventually, I realized that what I was actually doing was diminishing the importance of their in-game choices and removing a lot of tension from the game. The players knew they could always find out what might have been later. Which path they chose in the moment mattered less. And they could avoid risks and still learn what they might have found had they chosen to take the risk.

So I stopped doing that. The only way my players get to find out what's down that path is by walking it. The only way they learn what happens if they do something is by doing it. In short:

If the players don't go, they don't get to know.

Once I instituted this policy it made their choices somewhat harder -- but, consequently, more meaningful. It's improved their engagement, given them a greater stake in the decisions the group makes. And it's made the game world just a tiny bit more immersive. Just like the real world, if they want to know what's inside that cave, they have to go in. They're free to walk away; but then they won't know what's down there, if anything.

And doing this is really, really hard. I want to share! But I won't let myself.

To compensate for that, I've struck up a friendship with another DM so we can swap stories. They tell me about their campaign, and I tell them about mine, including the bits the players didn't engage with. It helps. But even now, sometimes I slip and let people know things their characters didn't experience, even though I know I shouldn't.

It took me a long time to learn this. I hope it helps some of you.