The difference is good karma is like money earned. You have a right to do with it what you want. But bad karma is like owing money. When you owe money you don't have a say in the matter.

STUDENT:

When you talk about karma in this way, it sounds too neat and structured. It sounds like a man-made invention. Is karma really set up like a banking system? I think of words like principal and interest and it seems a bit too pat. It also makes it seem like there is some standard of measurement for the severity of actions committed. It all sounds a bit hokey to me.

SHIH-FU:

The Buddha taught that there were certain questions that were inexplicable and unfathomable; and if people contemplated these concepts in hopes of coming up with answers they could become deluded or confused. One of these is to try to understand what the Buddha's mind is capable of. Another is to try to understand the workings of karma. Karma is difficult, in fact impossible, to fully and clearly explain. Yet, people insist on knowing more about it. They want crystal-clear, concrete descriptions to help them understand their existence and experience.

The point is, while karma is inconceivable, we have to come up with analogies to try to explain its facets. None of them does justice to the actual thing. This time around I used a banking analogy. If you don't like that analogy, I'll come up with another one. But all of them will be analogies, and all will therefore fall short of the real thing. As Buddhists, the main thing for us to understand is that our thoughts, speech and actions have consequences for our karma, in this life and in future lives.