Karma is a widely used term which people often use synonymously with good luck. While it may appear that a person who has good karma has good luck, this is not the case. Karma has nothing to do with luck. It is about the simple idea that we all reap whatever we sow.
Part of the reason that karma is misunderstood is because we tend to focus so heavily on the material world. By contrast, when we discuss insight meditation we are concerned principally with the mind. The most important concern of karma is the effect that our actions have on the mind because the mind has the nature of forming habits.
If we take one action or another, that action will of course have consequences in the physical world, but those material consequences are only the tip of the iceberg. The most important result from any action that we take is the fact that it will condition us to take the same action again in the future.
This kind of cause and effect is what leads us towards good or bad fortune because if we are in the habit of doing good things, good things will naturally flow from those actions. However, if we are in the habit of doing things that are harmful to others, then we will be continually met with the negative results of those actions.
The good news is that if we have built up bad karma by way of bad habits accumulated in the mind, this problem can be corrected through insight meditation. When we train ourselves in mindfulness we can become aware of the craving associated with our habits and allow the energy to dissipate. When we return to our daily lives after a retreat, we can therefore enjoy renewed happiness stemming from our improved karma.