In particular, the phrase ‘クソして寝ろ’. I’ve seen it translated as ‘take a shit and hit the sack’ while googling it as well as a bunch of rather grotesque caricatures but I’m not exactly sure what the phrase means, so to speak.
There’s a pixiv dictionary entry for it: くそしてねろ (くそしてねろ)とは【ピクシブ百科事典】
The meaning seems pretty literal - really just take a dump (have a bowel movement, elongate your spine, go number 2, pick a euphemism) and go to sleep. The origin appears to be a manga, though I’m not at all sure what the context for it is. That’s probably where the grotesque image you see comes from as well.
According to some page unearthed by Google it means:
“Go to the bathroom and get some sleep.” It is used for people who persistently complain or ask questions. It may mean, “Your opinion is as boring as a poo,” or "You are like a child to complain so much. If you are a child, go to the bathroom like a child and go to bed.
According to the link you posted
So, it means to just stop thinking about a bad outcome.
Okay, this seems to be the closest for the context I’m looking for, since there it’s one character chastising another. Only problem being that it’s also a callback to a previous scene where the second character took it as genuine advice rather than an annoyed outburst…
Translating stuff can sure get involved.