Why do men get so wound up sometimes?

Went to my weekly boxing class last night. We were only two, and our coach asked us to spar a bit.

I'm not that good, I still a lot of training, especially cardio, but I landed a couple hits.

After one of the hits, the guy starts yelling and complaint that I was hitting too hard...

I tried telling him I'm sorry if I said and that I'm not trying to, and he kept whining.

The guy isn't as tall as me but he's well built.

What does he expect in boxing?
Why do men get so wound up sometimes?
Post Opinion