If you stump your toe, and see it as an injury, you will be in pain, perhaps run to a doctor, and focus on the physical discomfort until it disables you, or at least severely interferes with your life. Karma is the system which returns to each of us, without favoritism, every act ever performed along our evolutionary path, and returns those acts in like kind. If we were abusive, we will be abused. If we treated others with kindness and respect, we will be treated in the same manner. To refuse to handle a tough situation, to deny your full potential, to neglect doing something that should be done will affect the physical body, the mental health, the emotional stability and even the affairs of life, and will follow you through each incarnation, until correct action is taken to balance that which has been avoided.
Every thought creates an alchemical process in the conscious mind.
The force of the Action is a direct result of the strength of the Thought and the power of the Will. Nothing happens by accident. We cannot deny responsibility for our actions. Everything simply changes form, and becomes a part of forever. Each of us has pure free will, whether we choose to exercise it or not.