Ok, first of all, we can all agree that some people are unable to do some things, right? If everyone could do everything, we would be gods, not human. And there should be no shame in admitting that some things are simply outside of one's capability.

Sometimes the person telling you that you can't do something is right. Sometimes they care about you, and they are warning you with the best intentions at their heart. It's not always about belittling or underestimating you. Sometimes it's like "Look buddy, this is not going to work out, and I'm warning you so you don't get screwed". We should not villanize people for telling necesary hard truths.