Life has its ups and downs. Busy times and quiet times. So does your fiction.
Non-stop action is good for an adrenaline rush, but as science will tell you, adrenaline rushes are, by their nature, short bursts of panic-energy that are designed to get you out of immediate danger. Not prolonged sessions of excitement.
Your own action scenes will have much more impact when you break them with quieter scenes of introspection and reaction. Give your characters time to comprehend the consequences of the action scenes, and your readers will also have the chance to understand their full significance.