So far I haven't. Most of my stories stop midway through when I can't connect the first act to the second, or the second to the third, and so on and so forth.

Of course, a technique I've heard of but haven't tried, and it sounds fun, is simple. Have a man with a gun break down the door, or something similar.

If you can't move on, have something big and dramatic happen that snaps you out of the third act slump.

What I do, honestly, is I talk to other people about it. I have a few dedicated "wall bouncers", one of whom is my wife, who I talk about my stories with. Sometimes that is the best thing to keep going.

Also set some goals, and make sure they're not too stressful, but still a little stressful. I tried setting the goal of posting a chapter a week... which worked up until I had to prepare for my masters defense.

Also, never worry about jumping around with it! I've started a story on the second or even third chapter before and gone back and finished.

If you'd like to talk more on this subject, I'm available.

One of the most effective means I've found for my own writers block is to think of the most random, exciting thing that can happen, and make it happen. Logic comes into play in two ways - you either try to make it somehow logical and befitting of the story when you write it, or forget the logic for now and worry about that later or during a revision stage.

Much of the time, the material I end up getting as a result of this becomes a permanent part of the story, even if the crazy thing I added ends up getting discarded. Going in an unexpected direction can have unexpected consequences, and often, said consequences end up being pleasant and useful.