I persevere. What I do to push forward depends on the draft I'm on. If it's the first, I make a note about what I'm having trouble with on the draft and continue with the scene. If it's the second draft, I fill in the gaps I notated as best I can, and take note of new ones. By the third draft, I usually know my setting and characters well enough to fill in prevalent information and remove superfluous stuff. I believe in pushing myself and not letting a hang up staunch the progress of my novels.