According to the Seth writing not punisment but a playacting that put the person in the different roles as he/she plays the other and how his/her behaviour impact them.
It litterally gives a different point of view on the same situation as you find yourself on the receiving end good or bad, all for learning purposes.

I suppose that it stops being operative once you grasp it, having lived it so the lesson is not just intellectual but etched into your being (the reason Seth gave for our living through all these experiences in the flesh).

Karma is based upon reincarnational lives following one another.

Seth tells us there is no karma. Because all our lives are simultaneous, we are not being "punished" for deeds done in another life. A hint of original sin here eh?

Karma also lends itself to "cause and effect", which Seth discusses as well. Cause and effect are based upon linear time, but because time is simulataneous it is possible for effect to proceed cause. Seth enourages us to set aside our "scientific eye" and not always use the same tools such as rational thinking and logic to define our reality. In this way we invite reality into our lives.

so many ways i can describe karma:
action and reaction
life curriculum
laws to resolve polarities
primary spiritual law of oneness
the reality we attract

karma is karma. good karma and bad karma are judgments that we put on events. good karma is still karma and we remain bound by it if we are judging it.

in yoga, and the study of the aryuvedic scriptures, i learned that the way to avoid "good karma" is to do everything, every act, out of service to higher power. call it god, or your higher self, or the universe, whatever, give it up to that. no sense of doership or earning brownie points, just duty to self, which is one in the same as humanity, the universe, higher power. just like we expect our red blood cells to do their duty.

what we call "negative" karma is attraction at work for a lesson not learned. when we have a negative (especially traumatic) inner experience, we can often find ourselves thinking or saying "no", "no way", "this is not happening", "i do not believe it", "not again!", or other words of denial. the energy under these thoughts and words compress the energy of the negative emotion into a tiny super-dense dark crystal. this dark crystal settles in the area of the physical body that is relevant, usually at a joint or other place where the energy vortexes, where it can remain undisturbed.

the dark crystal is the memory of the stored negative emotion and it wants to be realized. we are using our vital energy to hold it down, keep it compressed, and prevent its realization. the dark crystal works like an antennae to the ever-abundant universe, and it attracts the people, places, things, events, that will give rise to the emotion that has been denied. if again, we say "no way, this is not happening", or other posture of denial, then we now have another dark crystal of the same frequency which will move around through the body and settle into the relevant spot (responsibility issues go to the shoulders, sexual issues to the genitals, etc, (see louise hay)) and now the crystals have twice the attracting power, and so on. eventually we get around to saying, "why does this keep happening to me?". the good news is, if we allow the feeling to out fully, we can release all of these crystals at once, but more often it is like layers of an onion.

another thing these dark crystals do is block energy flow in that part of the body, because they are so dense, in the same way the sushumina (main energy channel) runs paralles to and in front of the spine. the bone is too dense, but serves as an attractor and its field a carrier.

i can sometimes feel these crystals, like a grit under the tissue, when i am doing healing massage. they can be worked out with massage, and the emotion may come up. they can be released through bringing healing energy through hatha yoga asanas. the crystals can be shattered by vibrational or sound therapy of the right frequency. there are many other ways too.

all accidents, injuries, disorders and diseases arise from these dark crystals and their attracting power.