Many of us fall in love with our characters. Like a parent, we want to shield them from arguments, injury, embarrassment, all the things that sensible people shy away from. If we devise a situation that gives our character pain, we take the action “off-camera.” Fight this impulse, writers! Fight it with everything you’ve got.
Look at a scene and ask yourself, what is the worst possible thing that could happen to my character at this moment? Enact it and see how your character deals with adversity. Make sure he’s operating with maximum capacity.
That said, it’s a wise writer that doesn’t swing so far that her characters resemble Job. Your readers grow fatigued with all that trouble. Astrid Magnussen in White Oleander is an example of the writer giving her poor protagonist too many hardships to overcome. Obviously that’s a matter of taste, and a lot of people disagree with me.
Vary the trouble. The reader's interest is piqued when your character is embarrassed, fearful or falls in or out of love. Readers love to be surprised.
To create surprise, look at your pivotal scenes and asks yourself what's likely to happen next. Then write the exact opposite of that.
When you finish your novel, chart the intensity of trouble and see what kind of pattern it forms. Do you have a rising sense of trouble as your novel reaches its climax?