We inherit a certain amount of bad resultant kamma from negligence and not knowing. We have probably blundered through life not being that clear, and so bashed into things and got bruised and knocked around. Then, on becoming a little more conscious in the present, we begin to experience the dents and the afflictions of the heart (citta). This is what we inherit, the vipàka.
So what can we use to push the dents out of the heart? What will repair its wounds?
In Buddhism, the emphasis is to create good kamma in the present moment; to do good. That engenders the strength to repair the damage, the wounds, or the afflictions from the past.
That encouragement requires an act of faith: faith that the state we are in now may be afflicted and negative but we can still bring around a goodness that will increase.
Of the images that the Buddha used, one of the most attractive and memorable is of a trickle of water running down a hill; how that trickles and goes over the crags and drops down the gully — and gradually other streams flow into it. That image presents something that was first of all just an insignificant little trickle, then it gradually accumulates, and as it accumulates it cuts deeper, and as it cuts deeper it attracts more water to it.
Just as a big river will attract other streams to it, goodness gets fuller and bigger until nothing is going to stop it. It gets so big it sweeps down to the sea; and there it can empty itself completely.
This reflection by Ajahn Sucitto is from the book, Kalyana, (pdf) p. 22.