Down regulating and emotions?

Can you explain what is happening in our brains when we’ve been over abusing sugar/drugs/chemicals… and then we stop cold turkey? The detox aspect of it is hell enough, but while going thru it… choosing ‘peacefulness’ feels like a huge stretch. But so does ‘curiosity’. Honestly, anger and rage at myself feels like the most appropriate, but I know where that also leads. Right back to abusing myself with this stuff.

I need a better understanding of what down regulating is and …is there an ‘up regulating’…? Or will I naturally ‘up regulate’ once the sugar, drugs, leave my system completely?