Destiny is Self-Made
"Kamma is "one's own", brahman youth,
beings are heirs to their Kamma.
Kamma is the womb,
Kamma is one's ancestors,
Kamma is the judge.
Kamma separates beings
into low states and high states."
Killing living beings leads to shortness of life-span;
abstention from killing leads to length of life-span;
behavior inflicting many pains leads to having many illnesses;
behavior inflicting few pains leads to having few illnesses;
ugly, angry, disagreeable, contrary, hateful, resentful behavior leads to ugliness;
being of pleasing disposition leads to beauty;
jealousy leads to being of no account;
empathy, happiness at the happinesses of others leads to being of great account;
stinginess leads to poverty;
generosity leads to wealth;
disrespect leads to being low born;
paying due respect to the respect-worthy leads to being high born;
failure to inquire leads to weakness of wisdom;
questioning the wise conduces to greatness of wisdom.
See also MN 136. Where the Buddha explains the workings of kamma: good deeds produce good results, bad deeds produce bad results in spite of cases where this law does not appear to be working.
What does it mean when the Arahant states: "Debt-free (anaṇa) am I!"?
When one comes to a complete halt, stops the world, ends own-making, makes no new kamma whether of mind, speech or body, what remains is only the results of old kamma. Old kamma is the debt. It is debt in the sense that Kamma is energy which, like electricity when it contacts the filiments in a lightbulb produces illumination needs an object to have an effect and is a force in nature out of balance until it is grounded out. The objects of kamma, the filiments, are the subjective mind and the five lower senses. No longer associating with body, sense-experience, perception, own-making or individualized consciousness, the Arahant no longer subjectively experiences the effects of returning kamma. There is no longer a subjective existing being there. His experience of such kamma that remains to be experienced to ground out is as of a detached observer. His effort at having detached himself from subjective existence is his having paid off his debt. This is the meaning of being debt-free.
See for example: SN 1.11.17
How do we reconcile 'kamma', which teaches that actions produce returning results that are hugely amplified with the law of physics that states that actions produce reactions which are equal and opposite?
By factoring in the force of the recipient's reaction or response plus the combined forces of all those that are influenced positively or negatively by the force of the actor's action on the recipient down through Time forever to the point where it is beyond notice.
We might say that if the pitcher's pitch represents the force of the action, then the force of the pitch, plus the response of the batter plus the reaction of the audience, boosters and detractors, plus the reaction of the team and the team owners, plus the reaction of the television sponsors, etc. etc. etc. down through Time represents the force returning to the pitcher. It is still in effect when some fan looks up ancient baseball statistics a thousand years later.
In this light, there is no deed, no matter how slight that is not significant. "Walk as one would walk who was with each step planting the seeds of the gold-fruit tree."