In my understanding, Karma is dues. So there is no good karma and bad karma really.Like there are no good dues.(The reason the blog address is goodkarma is because karma was already registered and goodkarma was available ) But good karma and bad karma help to explain concepts better rather than karma by itself.
So Karma dues get paid back through suffering.(Like a coiled rope will have to unwind to straighten up)
If you have karma,you have to suffer.
(I am not advocating fatalism or saying if you are suffering ,you must have done wrong in your previous birth and you deserve to suffer.I am stating that if you create debts in this life you will have to repay them back.)
If you have more karma,you suffer more.
If you create more karma in this life (through wrong thoughts,words or deeds) you will add to your suffering.
The corollary to this is if your dont create further karmas in this life,you will automatically not create any more suffering.
Old dues will slowly get cleared and additional suffering can be controlled.
I speak at the level of the individual.There are other forces at work at the level of family or society at large,which are far too complex to generalise .
But control karma and suffering CAN be controlled .