There is a need to preserve tension in battle scenes. Therefore, if the protagonist is strong, show battles from his foes' perspective.
There is a need to pull reader in with emotional scenes. Therefore, when creating one, write it as if you were describing a painting.
There is a need to give your reader relief with comedic scenes. Therefore, you need them short, and cut off from the drama.
There is a need to create suspense with drama scenes. Therefore, show the thoughts of your characters, make readers relate to their problems.
And there is a need for you in all of your scenes.
Create things you want to create; shape the world to your whim.
For you are the author of your tale.