>>7288479generally, body tries to upkeep a state of hormonal balance called a homeostasis
when you inject/imbibe some kind of substance that affects the homeostasis, the body has a reaction that counterbalances that, while also having another reaction that counterbalances the counterbalance, so you don't swing too hard into other side
when you ingest a substance for long enough time for it to create a tolerance (aka. your body basically figured a way to perfectly balance its presence in your body) and then stop completely, the counterbalance reaction doesn't just go away and tries to make up for the lack of said substance, causing things to go out of wack
depending on how addictive it was and how heavily it affected the homeostasis, this can range from some light symptoms/cravings (sugar, weed, caffeine) to shit that can actually send your body into a shock and kill you (opiates)
