I hear what you're saying. I have a real knack for not panicking in the heat of things - probably because I grew up as the stable emotional support for my lovely alcoholic/codependent parents. It's kind of surreal how calm and self-fortifying I can be when under the gun. I'm really good at carrying on while people are crying too (another lovely learned behavior) that has often caused me to wonder if I lack empathy.
But I will note: people can startle me. I actually tend to hide, because I find relaxing around people so difficult. It takes me a long, long time to warm up to someone and trust that they're not going to randomly explode on me. My job used to involve a lot of work in the bush. I'd take a bear any day to a random stranger; I trust the bear knows itself better than a given human being.