The words crackled off the page, there was energy and motion in the fight scenes, and suspense and tension prior to the fight's beginning. It was there because it was inside me when I wrote it.
Conversely, some of the pages I've written for The Mageborn Mechanic show how much I'm fighting with the story. Frustration just drips from the page (which works for some scenes, since the character is frustrated as well). I'm going to have a pile of work ahead of me, rewriting but I'm on the downward slope of the novel now. When I go back, I'm going to be asking myself what emotion I want in each scene. Try to shake things up and vary the emotional beats, try to make things more upbeat where I can without losing the tension.
Now, I know as an aspiring professional, you can't just sit around waiting for the right mood to right. But you can cultivate it. If you're writing a romantic scene, put on some music to set the mood. If you're writing a fight scene, go do thirty pushups or run in place for five minutes. Then see what you've written.
You might be surprised to see how your mood affects what you write and the words you choose.