The Law of Karma
Central to the philosophy of yoga is the universal spiritual concept of reaping what you sow: the law of Karma. Karma is the future consequences of one's current intentions, thoughts, behaviors and actions. While the Karma you currently create is the seeds that present future life experiences, your Karma is not your fate. You have the ability to consciously choose how you respond and react to Karmic generated events, thus reducing the current impact of your Karma and reducing or eliminating future Karma. This is both a psychological and physical practice, with the mental attitude much more powerful than the physical deed.
The law of Karma is connected to the constant changing physical world the yogis call Samsara, the spinning wheel of life and death. This wheel is said to have six spokes: virtue and vice, pleasure and pain, attachment and aversion. These spokes are the types of Karma that bind us to the wheel and keep it spinning. The goal is to break the spokes of Karma to become liberated from the mundane and suffering world of Samsara.
Good Karma is good, bad Karma is bad, but attaining any kind of Karma is undesirable. The goal, through the practice of yoga, is to stop the cycle of Karma by ceasing further Karmic accumulation. The yogis tell us the only way to not produce Karma is to act selflessly, without ego, without the desire for any reward. Liberation from Karma and Samsara is known as Nirvana, a highly esteemed spiritual state. But striving to attain a state of Nirvana is not a necessary goal; any reduction in Karma will improve one's life, well-being and happiness.