We all know that fibs works from time to time but not all the time like most TA stuff, commonly said. After some research and reading its seems to be "common TA knowledge" that every trend have the chance to retrace either;
1/3 or 2/3 of the main move.
It's also mentioned that a 50% retrace is significant so lets add this too.
This finally gives an explanation I can except and even use, which I couldn't with the fibonacci magical numbers. So I made my own retracement-levels on the original fibs indicator plotting 1/3, 1,5/3 and 2/3. I could plot 33.33, 50 and 66.66 but it seemed too like the damn fibs What you will see is that these numbers are close to the old fibs numbers used in trading 38.2 and 61.8, and of course 50, just with an non-magical explanation.
And no, I haven't tested this enough out, its just a theory. Let's use the great power of hindsight to "nail" my point lol, drawn from top/bottom of this down-trend;
Measure twice, cut once