Just because we don't proclaim it far and wide every step we take, doesn't mean we aren't heeding it. This is the beginning of the art we use every moment we train.
Note, this is the first lesson of the long sword: That you shall learn to make the cuts properly from both sides, that is, if you otherwise wish to fence strongly and correctly. Understand it thusly: When you wish to cut from the right side, so see that your left foot stands forward. If you then cut the over-cut from the right side, so follow-after the cut with the right foot. If you do not do that, then the cut is false and incorrect, because your right foot remains there behind. Therefore the cut is too short and may not reach its correct path below to the correct other side in front of the left foot.
The same when you cut from the left side and [you] do not follow-after the cut with the left foot, thus the cut is also false. Therefore note, from whichever side you cut, that you follow-after with the same foot, so you may execute all your plays with strength and all other cuts shall be hewn thusly as well.
(trans. Christian Trosclair)
Other masters and sources will tell us that we may use such false cuts, or false times, in order to gain certain situational advantages, mislead the opponent, etc. But in order to choose when to break these basic principles of the fight, we must first grasp them well.
11 Whoever goes after cuts,
They permit their art little joy.
12 Hew nearing, whatever you wish:
No change comes in your shield;
More sound advice with multiple meanings in different situations. If you go to strike after the opponent begins his strike, you will suffer for it -- you'll be pressed, it's harder to parry, etc. But line 11 of the original Merkverse has another meaning as well: don't chase after the opponent's sword. This basic advice is at odds with the concept of Nachreisen, but that's a case of "i before e EXCEPT AFTER C." The fencer must understand how to preserve his shield, i.e. maintain good cover of his lines, before he can venture out to travel after, striking in the Nach instead of fencing soundly in the Vor and in cover.
Fence only from the Vor, and you might do well until someone more clever exploits your sound but basic fencing. Even so, your sound fencing may serve you well if they attempt to be overly clever and neglect their basic fencing. A number of our own club's fencers stick with exactly this approach.
13 To the head, to the body,
Do not omit the harassing-strikes.
14 With the entire body fence
Whatever you desire to execute strongly.
It's no coincidence that these two lines are paired together. Many fencers take note of the admonishment to fence strongly in every action they take. But harassing strikes are necessary in order to make the opponent uncertain about which of your strikes carry your true intent to strike. All strikes, false or true, must be executed strongly so that they pose (or appear to pose) genuine threats to the opponent. But if you only commit 100% to every strike, you become predictable. You can strongly execute quick strikes at the hands, or slow strikes slightly out of distance to the leg, or all-in strikes to the opponent's head just when he thinks you're not serious about your next strike.
But we are warned by the masters about this: just be careful about truly making a false attack, b/c every such action creates an opening, a vulnerability for the opponent to exploit against you. Some of them argue against making false attacks. Others use false attacks extensively. And the remainder stress you must know your times of the hand and foot (and those of your opponent) very well.