Just because you have good kamma showing right now, as I said, doesn’t mean that the account isn’t going to wear out. You have many accounts, many different seeds, growing at different rates, ready to sprout.

"Even with kamma, the Buddha said that if you ask, “Well, the fact that I’m suffering this right now or that right now: Exactly what kamma did I do in the past that caused that?” his advice would be, “Don’t go there.” If you tried to trace that back, he said, it could drive you crazy, because kamma is so complex. The important things to know are the basic principles. One is that if you do something with a skillful intention — i.e., one free from greed, aversion, and delusion — the result is going to be happy. If you do something with an unskillful intention, the result is going to be miserable. And there are gradations. And because you’re doing things all the time, you’ve got lots of kamma.

Another thing he has you realize is that the fact you’re a human being means that you’ve got both good and bad kamma. And it’s also important to realize that not everything you’ve done shows up right now. There’s a mistaken belief that we have one kamma account and that what we see right now is the running balance. If the running balance is pretty good, we figure, “Well, we can just make it better and better, add more money to the account and we’re pretty safe.”

But the Buddha’s image of kamma is a field. In one of his field analogies, acts of kamma are the seeds planted in the field. Some of the seeds have sprouted already, the plants have grown, they’ve died. Others are in the course of sprouting: These are the ones you see right now. But there are a lot of seeds that are just sitting there in the dirt, waiting for the right time to sprout and grow. Which means that you don’t know what you’ve got in your karmic background. It may be that all the good seeds are showing right now, but the bad seeds will show up later. Or vice versa: Some people seem to be having lots of bad seeds sprouting right now, but that doesn’t mean there aren’t good seeds back there in the field.

And that’s as much as you need to know.

Here, too, the teaching is more of a sketch than a full explanation. It’s enough of a sketch to make you realize that you’ve got to work on your skillful qualities, and you can’t rest until you’ve discovered that there is such a thing as the deathless and you can verify it for yourself. That’s when you reach a measure of safety. If you haven’t reached that point yet in your meditation, anything can happen.

So keep that in mind as you’re practicing. If you find that you’re getting lazy or complacent, remind yourself that there’s no reason for complacency. Just because you have good kamma showing right now, as I said, doesn’t mean that the account isn’t going to wear out. You have many accounts, many different seeds, growing at different rates, ready to sprout. Sometimes their sprouting is going to depend on what you do right now, which is why it’s good to develop a good state of mind right now."

~ Thanissaro Bhikkhu "Karma & Rebirth: A Handful of Leaves"