You learn things by getting hit

Can you please explain what is "by getting hit" here?

It's not like when you learn something important, it's the best day of your life, it's often… the importance of what you learn is often proportionate to just how wretched it is to learn it. You know, you learn things the hard way, you learn things by getting hit, because obviously if what you're doing is working, you get what you want.