Karma is what it is, neither good nor bad. If our actions produce negative results we called it bad karma and actions producing positive results were termed good karma.
It is primarily our functioning that defined karma.
People with a sunny disposition and godly thinking always indulged in good karma, positive karma. Those indulging in vice always attracted bad karma, negative karma!
Karma can be labeled as the bookkeeper of the cosmic system, the accountant general of cosmos. Every single record of our actions, even in thoughts gets recorded in books of karma. One just cannot escape the bookkeeping by karma.
Whenever a thief indulges in theft unknown to anybody, one thinks one is safe. Yes legally one may be safe but what about the domain of God where all actions are accounted for. Externally, bodily we may be safe but what about the taint on our soul atman, the taint created by negative activity.
We must remember each and every single action of ours is getting recorded in the books of karma. If we do not meet our fate now owing to negative activities indulged by us, we shall do so in future, even future manifestations. One just cannot escape inscrutable law of karma. As we sow so shall we reap, nothing less or more.
We just cannot expect mangoes to grow on a guava tree. In the domain of God our good and bad actions gets recorded every single moment of life.
When people sometimes suffered out of blue, it was negative residual balance of karma from previous manifestations fructifying. A person winning a lottery all of a sudden is good karma fructifying.
A spiritual traveler makes sure that one does not attach self to fruits of karma performed. One neither attaches self to bad karma nor good karma. One always indulges in karma, nishkama karma way of life offering fruits of karma performed to God Almighty all the time.
Nishkama karma simply means working with an unattached attitude (never detached). Nishkama karma yoga does not produce any karmic bondage.