Well when things go too well or too badly I tend to quit the game and start another. Usually they go too well, which is damn boring. Sometimes I come up with a interesting build for the nation and start over.
I've always liked the idea of bleeding your opponent out of resources. Attack a province beyond the front lines, put some PD and pillage till its worth nothing. Repeat a few times at high pop or farmland provinces and you can win tough opponents pretty fast thus speeding up the boring end part.