Of growing up without realising it

I underestimate myself sometimes. I have had several occasions to notice this.

For example, I underestimate my strength. Several times already, I have hit or moved something too hard, harder than was necessary.

Now I wonder whether I underestimate my pain tolerance as well. And that could be dangerous. Because, as Doraemon says, pain is good. Without pain, you could die without knowing it.

Like when my whole arm was anaesthesized, I wouldn't even have known if someone chopped it off. Scary.

I think this underestimating comes partly from my complete lack of strength and total intolerance for pain when I was small. Knowing that you were somewhat inferior while growing up, somehow you just never expect it to change. For how do you quantify this kind of thing? How do you know whether you have improved? There are no results to show.