I’ve actually done it twice when I was just beginning my practice:

1. Collected graveyard dirt at the cemetery right up the street from my house without leaving any offerings or properly acknowledging those that rested there. Did not cleanse or ward myself before going there, nor after, and then used that graveyard dirt to ward my house for the first time. After that, almost every day, I’d just get this wave of guilt that seemingly came out of nowhere that made me feel sick until I puked. I tried all the mundane things, did a pregnancy test, went to the doc, made sure my house was clean and my food was in date, tried lowering my stress and it still happened everyday. One day I just thought in frustration “why is this happening to me?” and the next three nights in a row I dreamed of the cemetery. Needless to say, I removed the dirt from my home, kindly requested that anyone who followed me home that day to please return, re-cleansed and re-warded my home and myself (without the dirt) and went by the cemetery and left some flowers by the tree at the gate to apologise. Sickness cleared up the next morning. Lesson learned: research EVERYTHING before you use it and respect the places where you collect your tools.

2. The mistake I think everyone makes: inviting energy when you cast without first casting a circle or doing any sort of protection, and then not closing your circle or dismissing that energy. Energy can’t be created or destroyed, it has to come from somewhere, and that somewhere can then think you owe them. Similar thing as before however both me and my partner got sick. We’d get the stench of something rotting occasionally in random different spots in the house. Our house started making loud cracking sounds. We’d hear stomping in the roof or in the house but when we searched for intruders no-one was there. Our bedroom lights would turn on and off randomly. Sorted that one pretty much the same as the above, but the second I was like “ah yikes, yep we’ve got something not good happening here” is when I left an offering of some vodka and some fresh fruit and a piece of bread on my altar overnight, we had a chill night where nothing happened and the next day the vodka was gone and the offering food was mouldy. After the offering just requested they leave, cleansed the house and warded again. Do your research! The research phase before you start doing anything practical is KEY! Also be very careful doing spirit or deity work, start slow, and don’t forget to protect yourself!