Yeah I'm almost the exact opposite. I did a lot of martial arts when I was younger but never had any actual fights. Not serious ones. By the time I reached adulthood I had no idea how to act in either verbal or physical fights and was avoidant of confrontation. It's hard work but I'm gradually getting the hang of being present and holding my own in tough conversations. It's still very rare for me to get angry rather than just irritated, defensive or passive aggressive. When I do get angry it simmers in the background without any outlet, and either dies away or eventually explodes in a weird, unexpected way.

I was thinking more about people who grow up with very little, i.e. aren't sure if their parents are going to put food on the table that day. If you start out like that but manage to get a steady job etc..., I think it can be much harder to take risks like changing career or being assertive in certain situations.