Every author knows that pacing is an important aspect of every book. When events occur very quickly, it creates a sense of action and excitement. ...Or, it makes the book feel rushed. So if you're writing with a fast pace, you have to ask yourself: is it action-packed, or is it rushed?
Timing and pacing will make or break a book. You can use your words to make time feel as though it's passing slowly, or very quickly, in your story. When scenes are thick and heavy and events are occurring very rarely, time will feel as though it's passing slowly. When events are happening much more frequently and sentences are short and to the point, everything feels fast. Many writers use this technique to create action scenes, and drive the pace forward quickly in order to excite readers.
But when it's not done well, it just makes the book feel rushed. There's a very fine line between writing great action and dragging readers across the pages of your story. The difference between a great action scene and a rushed pace can be summed up in one word: emotion.
Even during action scenes, perhaps especially during action scenes, you want your readers to feel the thrill of it all. They should be pressured by the weight of the danger, shocked by every new turn of events, frightened that their favorite character will somehow suffer. You want events to come quickly and you want readers to be able to devour the words at a fast pace, but always remember to give them time to gasp.
And to process what's happening. When you're just firing out information and drawing with rapid strokes, readers don't have time to take note of the fact that Mark has fallen from a shoulder wound and Cara just hurled a rock at Dylan's head. You don't have to be flowery or overly-descriptive, but you should provide enough detail for readers to soak it all in.
If Mark falls from a wound, describe the burning pain. Let me feel his horror as he watches the rock hit the side of Dylan's skull. Now, shock me when Mark turns to see Cara staring at Dylan, having just thrown that deadly rock. Don't cram events into your sentences so quickly that four things are happening at once. Even in action scenes, it's okay for events to play out one at a time. In many cases, it's preferable.
So re-read those fast scenes, and ask yourself what you're feeling. Ask yourself if you still have time to gasp, and then you'll know if your work is full of action...or just way too quick.