Here is a paragraph out of The Satanic Bible, "Small wonder that the 'white' magician fears retribution after casting an 'evil' spell! Retribution, to the guilt-ridden sender, would be assumed, by their very conscience-stricken state!"
In other words, and personally, I wouldn't think anything of it. Secondly, if one is contemplating whether or not he or she would cast a malignant spell, then perhaps they aren't quite ready to send the proper energy required for the hex or curse, because it takes an intent that is not questionable, by the sender. The whole idea is that guilt devours oneself, or it can.