You cannot expect Perfection. (You technically can, but it
does not mean that it would happen.)
You will always stray a bit from your plans. This is because there are
always external factors you cannot see or control.
The nature of perfection is not intuitive; in fact, it is just an
abstract concept, and may not grasp/understand circumstances (or even
know them!) Perfection, statistically, is almost impossible, with every
single thing you try to maintain perfection is humanly (and
statistically) impossible...
A perfect score on an examination is theoretically possible, but only on a lucky day, because it's a finite subset of knowledge out of a finite syllabus. But pragmatically, you cannot know everything you wish to know, and there are great costs to doing so...
You can dream. I will allow for dreams. However, expect a bit of deviation. Deviation is part of life. So acceptance is good for it!
Yet again, I think it was due to the education system praising the "100%" score. This may lead to the fact that one feels confused because they literally cannot improve from here, from the perspective of mark-hunting! Psychologically this is called the Ceiling Metric, where the brain is paradoxically scared it cannot grow any more, and most likely will fall the next time. However, the tragic truth is that a full-merit person speaking out about their worries of being "too good" would sound a bit socially awkward, which may trap them even more in something like nihilism?
I find this repeated too often. This is when a mistake occurs. Oftentimes, this makes it worse! It's already known and proven, so one is just repeating an axiomatic truth! It's a bit dismissive, to say. Rather, yet again, isn't it just a statistical reality?