There are numerous “icons” that are commonly practiced by Shodo practitioner’s. These are often mutually shared/identified with other practiced “arts”. One of the more common one's, is the kanji for “eternity”(“towa”, or “ei”). This kanji is often claimed to possess all the essential strokes necessary for the practice of Shodo (presented in their most “basic” form). In the view of practitioner’s of “Iaido”(sword-drawing/cutting), or “Kendo”, this kanji also represents all the essential “cutting strokes”(in their most basic form). The numerous forms of Karate embrace various other kanji (as well as “Towa”) depending on the individually decided emphasis by/for their practitioner's.
The correlating factor between all these subjects, is the acceptance that the practitioner is only offered a “single” opportunity to perform a required action. In the case of the sword practitioner, if their “cut” is done incorrectly, or inaccurately, they may not have a “second chance”. The same is true for the karateka. These, and the numerous “other” martial arts, depend on accuracy and precision as well as their individual actions being performed “correctly”(and without the ability to “repeat/fix” a mistaken action). Shodo, only allows a “single” opportunity to perform each “stroke” of the brush(any attempt to “go-back” and “fix” a mistaken stroke, is rarely possible, and is always apparent).
For myself, and in the instruction of my students (in both “Shodo”, and “RyuTe”), the necessity of doing an action “the first time” is an essential attribute. Students (be they of “Shodo”, or some martial art), can often get into a melancholy state of having a “good-enough” attitude regarding their practice of their chosen field of study. The practice of Shodo can/will train the student to focus upon the required intricacy’s of the art (with the thought, that these attributes will be transferred to their “other” practiced arts).
The “mistake” that I see being made by many student's (be it in Shodo, or in the practice of a martial art) is that the student “assumes” that the motion (or the “stroke”) must be made exactly as the instructor performs it. There are numerous “details” of an action that need to be followed/performed, but as long as the “details” are being performed “correctly”, the action may appear(slightly) “different”, yet still be being done “correctly”. “Individuality” will (definitely) become apparent between practitioner's (be they “Shodoka”, or “karateka”), yet the “core” motion is still identifiable (as having been performed “correctly” or not).
It is common to observe a practitioner of Shodo, repeatably practicing the kanji “ichi”(“one”). This is arguably the most “basic” stroke practiced. It is utilized in the vast majority of kanji, and is often performed “incorrectly”(from the Shodoka's point of view). Ichi, is more than “just” a “straight” line. In fact, there is nothing “straight” about it. The stroke begins at a 45º angle, then motions upward, narrowing slightly, then curves to the right, while “thickening” towards the finishing position. The stroke is then “finished” with a “cleansing bounce”, and the brush is lifted to the left (letting the “tip” trail into the body of the initial crossing stroke). Though a “straight” line, could also be identified as representing “ichi”, this would be identified as (being)“flawed”, or “incorrect” (from the Shodoka's point of view). Just as “punching” is often repeatably practiced by karateka, “ichi” is practiced by the Shodoka(for much the same reason).