Imagine a huge offensive lineman standing in front of you, snarling "You ain't gettin' by me!" Passing this obstacle will lead you to a clear field of view, Freedom.... To do what?
Gettin by physical or emotional obstacles won't let your mind roam freely so writing can begin anew.
Characters or Plots hanging in the air, in their imperfection? You staring at your computer screen, knowing what must be done but not doing it? Taking a break is the usual advice given,"Put it away for a while..."
Don't do it!!!!
The problem lies in your innate "self honesty" and lack of willingness to beleive that there is a problem in your work. The tug of war between what you know to be right, and disbelief, that what you have created is somehow wrong or incomplete.
Try these two things:
1\ Take one character at a time out of your story and put them in another situation that somehow mirrors the type of charater you want he/she to be. Use a movie charaCter or TV show, and insert your character there. Pay attention to how your character would deliver a line compared to the actual actor. Look for hitches in you characters style of delivery, moment that you thought were strong enough to work will unveil themselves.
2\ Read a classic novel that is nearest to your plotline or character. Most Novelist base parts of their characters on reading experiences of their pasts. They fell in love with characters that they want to see more of, or feel they could be molded into a modern image. Reading a Classic or favorite novel will give you a mirror to place your character in front of, see how they stack up.
One of my favorite novelist, Patrick O'Brien, must have read every C.S. Forrester novel. He based his writing on a more accurate portrayal of Horatio Hornblower, which gave rise to Captain Aubrey. He saw a need to add the intellectual balance of Stephen Maturin and 19 amazing novels found their way to us. Master and Commander, which was made into a movie, is an incredible example to follow if you wish to see near perfect narrative voice and distance.
Find a source for intellectual drive, don't wait for it to just pop into your head or you could be waiting a very, very long time