I don’t ever recall feeling this way. In fact, I can’t imagine that I’d feel defensive or resentful if it did happen to me.
In the case of your sister, does she come out and say that “you are a moron”? I suspect that there is your sister’s assessment of your intellect and then there is your suspicion of her assessment of your intellect. You’re betting on the fact that they are the same. In my experience, the chance that you are correct is almost zero. And this goes for all of us. We have no idea what people think of us really. Shit, we have no idea what we really think of ourselves.
In a way, it doesn’t really matter. What harm is there in her explaining something to you? Do you feel your sense of self grow and get into defensive mode because the explanation is an attack on who you are? If this is the case, it has little to do with your sister and much to do with whatever you’re trying to protect. If your worth is dependent on everyone knowing that you are brilliant and don’t need an explanation, it would be best to proactively announce to everyone you meet what you know and how well you know it. Most people don’t know precisely what you know and don’t know. And in some sense, neither do you.
What if your sister’s explanation isn’t her best attempt at teaching the ignorant, and really just an attempt to connect with her sister by expressing her understanding of a subject? What if she respects you and wants the experience of bouncing her understanding off of someone who may be able to help expand the understanding or challenge it? What if it’s just a way for her to make sure she understands? Many of us – even here – find that our thoughts just appear when we are attempting to communicate them to someone. And the process of attempted interpersonal communication is also intrapersonal communication. The best way to know what we think is to allow our minds to tell us – through communication.
The thing is, in the case of your boss, this happens all the time. It sounds like you were not meeting her expectations. Her explanations were likely attempts to explain specifically what it was that she expected from you. When the expectations still fall short, the write-up is the next step, and eventually a firing. Whether or not you felt you were doing the job well, she didn’t. That could be the result of a real divide between your perception and the actual performance. Or it could be just someone who hated you and wanted to get rid you you. Either way, that type of clear communication in a workplace environment is a good thing. Imagine if she hadn’t explained in embarrassing detail what she expected from someone doing your job, and then you were fired.
If the difficulty in communication with your sister is merely practical (it takes too long to listen to this stuff), then just tell her the truth – you don’t have the time. One of the most frustrating things I experience in communication is when someone cuts me off to tell me that they already know something – even though it’s clear that they don’t. I’ve had whole relationships built on this, and it’s exhausting. In these relationships, there was also plenty of “I know what you think of me” going on as well. It was like dating a mind-reading mystic who hasn’t figured out that there’s no such thing.