I don't think I've ever been so completely wrong.
After charting the pattern on graph paper (it took me seven tries to get it right), I realized just HOW complicated the Scouting Legion logo was. And then, to make things worse, I had to make the scarf it was attached to ten feet long. Three skeins of green yarn and a severe hand cramp later, I finally finished the piece. It only took me two months, which was longer than I had originally thought, but not as long as I thought it would take once I realized the full gravity of my situation.
Despite my near-breakdowns, I am extremely happy with the final product. It's not something I'll probably do again any time soon, but at least when I do decide to do a piece like this again, I'll have a better idea of what exactly I'm getting into.