I have cursed a couple people in my day. The rules are simple. You have to be actively engaged in doing me or mine harm or you have to have done so much negative in my direction so many times that I have a very reasonable suspicion you will come after me or mine again. I have never cursed anyone that I have ever called friend, lover, companion or anything like that.
A some point in the past, someone tried to end my career. This was not unusual for this particular person and she had the power to ruin my work life permanently.That person no longer works where I work. I found out later that someone else instigated that situation for what reason I do not know. However, I did remember the words of the spirit I used for the previous curse in which he said not to call him for the next one. So, even though this person had gunned for my job and lost the battle and I thought her in a position to launch another effort, I did nothing.
I recently learned this person has a close family member that has just been diagnosed with a terminal illness. Had I cursed this person, I'd have wondered if my spell worked by impacting a third party. Many magicians would not be bothered by this at all. Many would make very logical arguments that would defeat my position. Good for them.
As a magician, I must know myself. I would not have done well thinking I caused such a thing. Nor would I have believed spirits that told me it wasn't my fault as I'd think I was just hearing what I wanted to hear. The decision not to curse saved myself some emotional turmoil.
I will make an offering to said spirit to thank him for the warning.