First is the pit of trying to do something. You aren't actually the agent in the chapter. You are the storyteller. YOU shouldn't be trying to do anything at all except capture what X, Y, and their buddy Z are doing. It's okay to have an idea of what you want to have happen and how. It's necessary. Just keep your perspective. The characters are in charge of the chapter, and if they refuse to do something you thought you wanted them to do, don't twist their little imaginary arms and make them do it. They'll rebel and get revenge later.
The second pit is right next to the first. It might even be a branch of the first, connected by a little underground tunnel. It's the pit-of-not-having-a-plot.
Wait, aren't we talking about chapters?
Yes, self. Even chapters need to have plots. More specifically, they need to have goals. Whose goal? Not yours, oh no, not yours! The characters'. Usually it's the POV character's goal, but not always.
Note to Self: Before you start working on a chapter, write down the goal and whose goal it is. Keep it specific and limited to that chapter, not something like "defeat the bad guys." Through the chapter, that person works towards that end, and they either make it, or they don't. At that point, STOP WRITING! That's the end of the chapter.
It's okay to have characters reflect a little after they do or don't reach their goal.
In fact, on further reflection, also make sure the end of the chapter sets up the next goal. Don't give them everything, or where's the rest of the story?
(I'm pretty sure I learned all this from Janice Hardy. She's brillianter than I is.)