O que significa now if you'd like to finish that cliche you followed me to piss or unload...Better not involve my reflection. I'm sleeping at night? How do I do it?

What's the meaning of 'better not involve my reflection'? ?

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This is a great quote, but it is difficult because it's a reference to an English expression that you might not know.

This has to do with the expression, "How do you look at yourself in the mirror?"

Which is a way of asking someone, "How can you be so terrible that you are fine with seeing your own face when you look in the mirror." or simply, "How can you be so horrible?"

So when he says "(it) better not involve my reflection", he means, "If you're going to criticize me, don't use that one cliché expression about looking in the mirror, because I feel no remorse about my actions."

We know that this is the correct interpretation because he also says, "I'm sleeping at night."
This comes from an identical expression, which is, "How do you sleep at night?"

Which means, "How could such a terrible person sleep peacefully at night?"

The character speaking is fully aware of these expressions and cliches. He is ultimately saying, "Alright, if you want to criticize me, do it. But, do know that I feel no remorse about my actions."