Pacing is how fast or slow the story is moving.

ID 28391540 © Nucleartrash | Dreamstime.com
The key, of course, is how to find the right balance. You don’t want the story to feel rushed, but you don’t want it to drag either.
I like to think of each story as a map. Each place along the way is a scene I’d like to put into the story at some point. The key is how to get from one point to another, and how fast I should do it.
One thing I’ve noticed is that there is a rhythm to each story. There’s the beginning where you’re establishing the character’s world. This is the springboard from which the journey begins. Also, you know there will be an end. This is when everything is resolved (happily or not).
It’s the in-between that will establish the pacing.
From the moment the character figures out his goal, the journey officially begins. He will need to come across obstacles along the way. Each obstacle is a pin on the map. These obstacles are your high intensity points where the tension is thick. Between the obstacles are periods of rest. These periods of rest allows the reader to catch his breath. It’s a low period of action.

ID 23847156 © Hermin Utomo | Dreamstime.com
Each obstacle (high intensity scene) gets bigger and bigger as the story progresses. The reason it gets bigger and bigger is because you’re heading toward the climax (the highest point in the entire story). You want enough space between the obstacles so that the story runs smoothly along.
It keeps the reader reading without making them think, “How did we get to point B so fast?” Ever have a time in your life when it seemed that everything that could go wrong did? And it hit you all at once? You had no time to step back and regroup. It seemed at every turn, you had a brand new emergency to deal with? Well, you don’t want to do this to your poor character in the story. It’d be jarring to the reader to have to have a “highly intense” scene back to back.
Also, you don’t want the reader to think, “When will we finally get to point B?” Ever had a time in your life when you were bored, bored, bored….and booooorrrreeeedddd. You were waiting for something to happen. One good memory of this was waiting for Christmas Day as a child. I don’t know about you, but December was the slowest month of the entire year when I was a kid. I thought for sure the 25th would never come around. You don’t want to put your character (or your reader) through this, either. So adding scenes into the book that do nothing to advance the plot need to be thrown out.
The balance can be a bit tricky to figure out. A quick rule of thumb I use is how I’m feeling as I’m writing the story. After an emotionally charged scene, I’ll allow the character to take comfort with a friend or family member. When I start to get bored of the “comfort” moment, I get things set up to get to the next emotionally charged scene. If I’m writing and I think, “I need a break from all this drama,” I’ll know it’s time to insert a “comfort” scene.
Hopefully, I did a good job of explaining it.
I understand exactly what you mean. I have to be very careful because I tend to want to get to the point too fast.
Sometimes I have jumped ahead to the next scene, just to get to the good stuff. Then I’ll go back and fill in the gap. I can’t jump too far ahead, though, or the stuff I fill in ends up changing the future scene. (This is another reason why I can’t plot. Things change too easily!)