Kamma is a very important topic. Wholesome Kamma are actions, speech and thoughts based in non-greed, non-aversion and wisdom. Unwholesome Kamma are actions, speech and thoughts based in greed, aversion and ignorance. I often tell a little story about Kamma that is very helpful for many people to understand how they can lessen the effects of their past bad Kamma. Suppose you have half a glass of hot water and you dump half a glass of salt in it and stir it up. The bad Kamma is the salt and you are stirring it up. Would you like to drink it? It would be pretty salty, wouldn't it? Nobody would want to drink it. Now suppose you have a bath tub and you pour the glass into the bathtub, and then you start adding gallons and gallons of fresh water to the tub until it is full. Do you think you can drink it then? The salt hasn't been taken out, but you have diluted it. So it really does depend on making lots of good Kamma in this life so it dilutes whatever bad Kamma we have done in the past.
When the past bad Kamma comes, just like Kisagotami, you can use it to develop more Compassion and Wisdom. That is using you past bad Kamma for benefit. Lot of times when the past bad Kamma comes, when Dukkha comes in our life, we push it away. However that just creates conditions for more bad Kamma. So we have to learn how to use the Dukkha, or the past bad Kamma, that is arising.
I have another little story called "Good luck, bad luck, who knows?". For Kisagotami, the bad Kamma she suffered when her son died, helped her find the path that led to the ending of all suffering. So if we can view our past bad Kamma in this way, any Dukkha that arises for us is an opportunity to grow. At the same time, rather than just waiting for the bad Kamma Dukkha to come, we can add lots of fresh water to the bathtub. Diluting it, diluting it, diluting it. We make causes and conditions for more good Kamma to arise. Then we can depend on the forces of our good Kamma to support us rather than just live in fear of our past bad Kamma.
Here's the "Good luck, bad luck" story: There was once a farmer who had a stallion workhorse. The horse worked very hard plowing the fields and transporting the goods. One day the farmer discovered that the stallion had disappeared. The farmers neighbors exclaimed, "Oh what bad luck, oh what bad luck!" The farmer simply said, "Good luck, bad luck, who knows?" The next day the stallion still had not returned and the farmers neighbors continued to say, "Oh what bad luck, oh what bad luck!" The farmer simply said, "Good luck, bad luck, who knows?" The next day the stallion returned, bringing with him seven wild female horses, the farmers neighbors exclaimed, "Oh what good luck, oh what good luck!" The farmer simply said, "Good luck, bad luck, who knows?" The next day the farmer's son was trying to train one of the wild horses and fell off, breaking both of his legs. The farmers neighbors exclaimed, "Oh what bad luck, oh what bad luck!" The farmer simply said, "Good luck, bad luck, who knows?" The next day the army general of the province came around drafting all able-bodied men into the army to go off and fight a very unpopular war in a different province. Of course the farmer's son was unable to be drafted. Good luck, bad luck, who knows?
So looking back on your own life you can often see that experiences which were unpleasant contained within them valuable learning experiences and were the beginning of a new direction for you, helping to lead you to new understanding. No experience needs to be thrown away and your bad Kamma, just like Kisagotami, can be used for inner growth.