I've heard some say a model railway is never quite complete. Sometimes it's a scene that doesn't quite look right, or a track arrangement doesn't quite work out operationally the way it did on paper. Or maybe that West Siding Switch is six inches too far east and it's buggering up train meets. Perhaps you tried to cram too much track into a particular spot. Hell, I'm sure there are thousands of modellers out there that thought;
"Finally, the layout is fully sceniced. I can enjoy the fruits of my labour",
..and then a week later some joker introduces static grass to the world. Man does that stuff look real or what? Would you start scenicing your layout all over again? I imagine I would.
Back on topic - sometimes the best laid plans don't work out they way you wanted them to. Port Hood was a good example of this, in that I had designed it poorly. What I had originally wanted, was crews to be able to leave the passenger portion of their mixed trains at the station while switching the Co-Op, but the station was in-effect on the run-around track. Well that's no good. I needed both sidings to be on one side of the main line to facilitate this. Luckily I hadn't secured any of the structures just yet, so all I had to do was salvage the track - an easy task with 99% isopropyl alcohol and a putty knife.
Back to a clean slate.