A) your textbook is wrong (for the textbook should provide you with the most useful manner of performing the form) -- in which case you have discovered a serious deficiency in the style you are studying (hence my irreverent comment about starting your own style)
You know, I'm not certain I agree.
For the most part, I tend to equate "textbook" with "formal". We (ITF) have a literal textbook - Magic Rub is probably intimately familiar with it - General Choi's "Taekwon-Do", the Condensed Encyclopedia (frequently referred to as
the Bible), or the more detailed 15-volume Encyclopedia.
I'm personally far from a hard-core pragmatist. I fit much better into the "artistic" category. My own specialities are Patterns (tul, our equivalent of forms or kata) - particularly the teaching thereof - and Taekwon-do's forte of fancy multiple flying kicks (ridiculously impractical for self-defence, I'm the first to admit, but fun nonetheless). Which is not to say that I eschew practical self defence, or breaking, or sparring, but formal technique is what interests me most.
But the formal method is
not what I'd use in a self-defence situation, particularly for hand techniques. I agree with Wolvorine that a formal punch, textbook stance, off-hand returning to the hip, etc, is somewhat impractical.
I
do feel, however, that the formal technique is vital... especially for a beginner (no matter how talented). To me, the formal technique is... an exaggeration, I guess you could say, of the important principles. The use of hip, or body, or the off-hand, which are all directly linked to the effectiveness of a 'practical' technique, but which
in that practical technique are incredibly subtle, can be far more easily demonstrated, taught, and corrected in the formal technique.
As a fourth dan, I'm still finding how subtleties in formal techniques apply differently to patterns, to sparring, to breaking, or to self-defence applications.
And I have to agree with Tacky's baseball-swing analogy, with apologies to Wolvorine - you may know your body's natural positions, but a lot of the subtleties that do increase effectiveness of technique can feel decidedly
unnatural until they've been practised for some time... and they are finicky enough that a green belt partner could miss their rpesence or absence.
As with Barsoomcore, I'm not defending the teaching ability of an instructor I've never met... but I
am defending the value of formal movements that, in their pure form, have no direct "street" application.
-Hyp.