you've been socially conditioned by your culture to have a kneejerk reaction through emotional response to certain activities and events and you default to them by instinct because hey the majority of serf minded people had to go somewhere after that ended, you learn these without effort because that's just how you're built you think it is some gods gift but it leaves you blind in one eye and no matter where the tide goes your moronic brain will follow just look at the world around you to this day and you can see the downside of unconsciously learning to follow social norms without ever questioning any of it, your emotions are fed to you by media and peers and you learn to mimic them by instinct, you're the same as the rest of them except they just never learned it without effort and when they do learn it consciously they suck at it because things need to make sense to them so if for some reason the status quo is beyond logic and fucked up they naturally resist adopting that world view that's why they are ostracized, they used to be integrated out of pity but the tide shifted and now they're being pushed out as the odd ones out which lead to wider scale issues within the system
tldr; you don't sense external emotions you mirror them via instinct because you're brain was wired like that to do it without any effort