The what of what? The whole idea of self-defense is that there are no rules, right? Bad guys do bad things and you have to do bad things to stop them? If there are no rules, how can there be etiquette? To be sure, one of the issues we have with students is that they tend to practice techniques a certain way. For instance, blocking with their left hand, and counter-striking with their right.
Countless times I've seen a practitioner demonstrate an extraction technique where an attacker has grabbed the student's wrist; only to have the student spontaneously, pleasantly, with hand gestures say, "No, grab the other wrist." And the faux bad guy does it, sometimes apologizing! Yeah, that's real - just like in the dark parking lot. "Hey lady, give me your purse." "Oh geez, would you mind standing over here when you say that, my left leg kicks better." "Oh sure, sorry."
But what we're writing about here is not fighting or extractions (Ho Sin Sul for the initiated), rather, this is about sparring. Sparring is to fighting what priming a wall is to painting. You cover the same stuff, but your goals are different.
The purpose of sparring is to practice one thing and only one thing. Timing. Period. That's it. Everything else that you need when fighting you can get in other ways. Easier, with better results. Want to learn how long your arms and legs are? Punch a bag, a board, or a brick. (misjudge the punching distance to a brick wall one time and see how quickly you learn the length of your arm!). Want to learn how much power it takes to crack a rib (about 3 lbs), then break a one-inch thick, one-foot square pine board.
Do you want to perfect your aim on a jump spinning back kick. Use a practice dummy (we call ours, Bob). Yes, everything you need to practice relative to fighting can be achieved without a partner, except for one (cue caveat music). Timing. Learning when to initiate a strike, block, or kick is very difficult and separates the novices from the experts. (what exactly is caveat music?) Watching a good fighter is seeing beauty in motion, no wasted moves, no wasted energy; just graceful movements and then, POW, strike, fights over!
As we learn to fight through sparring, we tend to hesitate when we should move and we move when we should hesitate because we misjudge the actions of our attackers/partners. After many repetitions, and practices, and sparring sessions we become more comfortable with the process, settle down, and begin to understand the give and take, back and forth; the dynamics of the fight. It is then that we can employ timing to both attack when the opening presents itself and wait when it doesn't.
(Caveat music commences) Now some will say that 'seeing' an opening is another benefit of sparring that cannot be achieved another way. Depending on what the definition of is is, I can agree or disagree with that perspective. Just about every sparring student I've had, from their earliest days as a white belt has said they just weren't fast enough to take advantage of a scoring opportunity. So, they didn't need a lot of practice to know where the opening was, it's just that they couldn't feel it coming (a timing issue), couldn't react fast enough (a timing issue), was too close or far way (moving with your attacker is a timing issue), or couldn't figure out the right technique to use (a timing issue - too much data to synthesize quickly).
So... what does timing and sparring have to do with etiquette? Remember etiquette? This is a posting about sparring and etiquette. Sparring is not about knocking teeth out, hitting with force, or even winning (although that's always nice). Sparring is about practicing timing. The goal is to improve your ability to spot openings, determine a suitable course of action, and then implement a technique without actually injuring your (get this next word here) partner.
So if in your overzealous attempt to get the hit in, you over estimate the distance or power; stop, bow, say you're sorry, and restart the match. If you feel you're vulnerable and your partner doesn't notice; stop, explain the opening, and restart the match. Once you realize that the goal is to learn (and teach) timing, your perspective will change - you need a partner here, not a duffel bag, a mirror, or a board; you need a live human being whose goal is to make you better. Courtesy should be a close cousin to the effort and sincerity of your workout.