Your scenes (in a novel) must do one or more of the following:
- move the story through action
- characterize through reaction
- set up essential scenes to come
- sprinkle in some spice
In addition to these purposes, each scene must have a degree of intensity. This doesn't mean equal intensity throughout. You don't want the cartoon feel of a coyote chasing a roadrunner in every scene. But something does have to be at stake in the scene; something has to matter. Even when the characters are taking time to breathe or reflect or regroup, the underlying story question needs to roil, like the bad goo under the streets of New York in Ghostbusters II. It is best to approach scenes as primarily involving action and reaction, setup, and spice.