Suffice it to say, it freaked out. I wasn't used to people sharing their feelings with me. In normal relationships, by the time someone is telling you they feel <insert negative emotion>, a ton of scar tissue has already been built up, and they're at a breaking point. So I was conditioned to believing that sharing feelings = things have gotten really bad.
But early on she would calm me down, and say no, things aren't bad, she's fine, she's just into sharing feelings early and often to prevent the buildup of resentment. So I got used to it, and even started doing the same thing back.
Eventually our relationship ended, but I brought the practice to new relationships I entered afterwards. And, unsurprisingly, it kind of freaked people out! Almost nobody is used to it at first, just like I wasn't. It's incredibly easy to get defensive when someone lets you know that they felt bad in response to something you did. And it's usually vulnerable and risky to find the words to share feelings without arousing the other person's defenses.
Still, when I look back at how I've evolved as a person, I credit this "scar tissue" view of relationships with a lot of personal growth. It's given me a habit of confronting people problems head on, something past-me was unconsciously avoidant of. An ounce of prevention is worth a pound of cure, and being willing to have uncomfortable conversations instead of kicking the can down the road is one of the hallmarks of adulthood and maturity.