Why is Hamlet apologizing to Laertes?

Hamlet is apologizing to Laertes because he hasn't been in his right mind. He is asking Laertes for forgiveness based on the fact that he has been mentally ill.

"Give me your pardon, sir. I’ve done you wrong.

But pardon ’t, as you are a gentleman.

This presence knows,

And you must needs have heard, how I am punished

With sore distraction. What I have done,

That might your nature, honor, and exception

Roughly awake, I here proclaim was madness."