When instructions are given, that is the beginning of a chain of events which lead to the finished task, and during this period certain things may not be able to be done, fully done, or are fully done the prescribed way, which lead to the end result being different from expected. When we expect things in a certain way we can want, yearn, and desire that way and that way only, anything else may be good, but not perfect, this in one of its forms of expression is attachment to rites and rituals, a depending upon what is done, or specific actions and results, to bring a degree of happiness and fulfilment.
As said at the beginning how instructions are given and understood may not be the same, and the difference is due to our own preconceived ideas, or notions, of what is, and the meaning we personally attribute to things, this is true elsewhere also, we see wholes where there are many parts, ignore certain unappealing aspects of things we like, or exaggerate unappealing aspects of things we don't like. This can be clearly seen in how we can find one person attractive yet another repulsive even though each has the same parts, these parts are not identical, and may fit together slightly differently, or have different proportions, although, they still both have the same parts.
It is the delusion that what we like is nice and what we do not like is horrible that deludes us into thinking these objects only have this one sided aspect, leading onto a diminished receptivity of the opposing side, how often do we pay attention or exaggerate what we like and ignore or undervalue those things we don't like, for no other reason than a preference?