caffeine has the worst withdrawals out of any drug
i am speaking from personal experience. i have been addicted to caffeine, nicotine, weed, and opiates and tried pretty much every other drug. i love drugs and hate life so i don't plan on quitting but i have had to stop all of these cold turkey at one point or another, and use the more harmful ones more moderately now. here is my experience:
weed is considered the least severe, i love smoking weed but the worst that would happen is my appetite being reduced, feeling depressed and having a hard time sleeping for a few days, and it makes me want to get absolutely sloshed on something else which i usually have no desire to do while high.
opioids are hell to get over, you will have all of the above symptoms along with diarrhea and much more intense mood swings. also a lot of physical symptoms like shivers, feeling like you have a cold and minor headaches (not as bad as caffeine withdrawal). they also tend to fuck with your thoughts a lot, like thinking about every time you've been wronged or people you don't talk to anymore
nicotine is nothing compared to the other two, and i know some dumbass in the comments is going to say "but weed is not addictive like nicotine is" but you'll feel a bit irritable for a day or two and that's it. the cravings get pretty bad but if you have no access to it you'll manage just fine. i'm on a vacation now with no access to it but i'm looking forward to smoking some when i get back. it helps tremendously with my regimen and my body doesn't tolerate alcohol so it's a good social lubricant. i will quit when i have children because i want to set a good example
now for what you've all been waiting for, caffeine. i've been doing this one the longest so that's probably why i have the worst withdrawal symptoms. i drank caffeine this morning but didn't this afternoon and i have the worst migraine, it actually makes me want to die. loud noises feel like someone is hitting my head with a hammer and i'm extremely sensitive to light. it feels like i can't think and i get absolutely nothing done. on all the other drug withdrawals i could at least be social and cordial but missing a caffeine dosage makes me need to lock myself in a dark room and pray to god. i already had a bit of a migraine this morning so it could be something else but this feeling is all too familiar. i don't usually get headaches if i don't consume caffeine in the afternoon, but if i don't drink any in the morning it is practically guaranteed. the longest i've been able to make it is 3 days before i throw in the towel because i'm miserable to be around and my head feels like it is imploding.
anyways those are my thoughts on addiction. i've tried quitting caffeine on numerous occasions or at least tried to lower my tolerance (i usually drink around 200-400mg a day) but had no luck. kudos to all of you persevering through this but personally, i don't know if i ever will.