.. my teacher taught me that if you take revenge, you have to start by digging two graves.

[ Daniel smiles a little bit at Ken as he says it. It's not really a happy smile, but.. more just a reassuring one. It says that he understands the gravity of the situation, but that he still wants to give something just a little hopeful to the poor kid. ]

It means that you're only hurting yourself as well if you try to take revenge. The bad thing is that you always realise that a little bit too late, huh..? [ The way Ken did. Only hurting after the fact, only realising by then how meaningless it all was.

By the time it was already too late to take anything back. ]

Especially when revenge seems so.. tempting. Especially when you have nothing else to fall back on in times of grief or pain.

[ I understand.

That's what he's trying to say. Mostly because he feels that's what always helped him the most when he was younger - whenever mister Miyagi, rather than judging him, just showed he listened. That he understood. ]

That you saw how pointless it all was afterwards shows that you're a good person.