It’s not irrational because you are also aware, as you’ve talked about it before if I recall, of the concept of “backlash”. You should have noticed that while there are mages who didn’t get backlash, there are even more mages who’s curses did nothing, did very little, or had more or less backlash.
People are hard to curse because they don’t want to be cursed, the people around them generally don’t want them to be cursed, and your will may not be enough to override that.
So if you want to call yourself logical, stop beating yourself up over an obviously false assertion. Backlash exists, its a risk, and the reasons for it are many and understood, mainly to do with protections on the target.
Divination is usually advised to look for protections before randomly flinging a curse for this exact reason.
Nobody’s pendulums are 100%. That’s not how being psychic works especially if the target has an emotional component, which it does here. Use a more intuitive method or take blind reading many times and take an average. I’ve explained how to do that before with envelopes hiding the answer.
Maybe this wasn’t an excuse, but you following your intuition and you were right? You don’t know.
There are other ways to remove yourself from bad situations than cursing. You could bless these people and attempt to heal them so they change, for example. You could use honey jars to make them like you. You could do domination spells to make them careful of you, there’s a lot you can do if you think about it that isn’t a curse and gets results.