Incorrect. Karma is not a good/bad system.
The way I've best heard karma described is that your soul is like a block of clay. Every time you do a particular kind of action it's like pressing into the clay in a certain way. Each individual action will therefore only do a little, but if you keep shaping the clay the same way for a long period of time, it will eventually begin to form into something else. If you consistently act dog-like, your karmic clay will be slowly molded into the shape of a dog by each of these dog-like acts. Unless you actively choose to someday stop this dog-like trend, your karma will make you into a very dog-like person and when you are reborn it will be in the form of an actual, physical dog.
You're obviously much more complex than acting only in a single way, but you undoubtedly have certain aspects of your life and personality traits which are more influential in your life, and those things will therefore be of the greatest karmic importance.
The concept of karma comes from Hinduism, and through it Buddhism. If you'd like to know more about karma, that's where to look.