One day, many years ago, I met a warlock I admired greatly. His knowledge of the world and the people in it greatly exceeded my own and I was determined to learn from him. Luckily, he was very generous and spoke with me at length about magic and how it works.
But when he told me about a curse he had thrown and how he put his victim in the hospital with it, I interrupted him. "Aren't you afraid that will come back on you?" I asked. "Don't bad deeds come back to haunt you?"
He sneered at me as if I had insulted him and said, "Dear son, if you are ever to practice magic you must learn one thing and learn it now. That good and evil are just like right and wrong, they're ideas that are as individual as fingerprints. Hardly a deed done in the world has been evil because the doer has always thought it just. Never throw a curse you believe to be unjust and it will never come back to haunt you."
With that he turned and walked away.
Many years passed, I grew older and wiser. I went to college and even got engaged to a wonderful woman. However, a blonde girl with too much energy and too little brains kept trying to come between my love and me. Even after subtle and not-so-subtle hints she continued to pursue me with greater and more irritating vigor.
One day, she wouldn't leave me alone and wouldn't even listen to what I had to say. I stormed home, remembered the warlock's advice and threw my curse. I threw it without remorse, regret or caution for I was in the right and there was no room for such things.
The next day, the girl fell ill with a mysterious lung ailment and was forced to miss most of the rest of the semester. She found herself very far behind and failed most of her courses. Rumor spread that she was even thinking about dropping out.
Soon thereafter I saw the warlock again. He somehow remembered me and asked me how I was doing. I told him, "I threw a curse just as you said. Because of it, a beautiful, friendly and sociable girl fell ill, missed class and may have to drop out of college. But I was within my right, I knew it then and I know it now. It has not come back to haunt me and I don't fear it will."
The warlock smiled and said, "My son, you are well on your way." With that, he turned and walked away from me, never to speak to me again.