When I've stopped caffeine, I get nasty headaches that make me feel as though there's a hole in my brain, or that I've been stabbed in the neck. Sometimes both at the same time. It's so fun!
For awhile my coffee addiction (only two normal cups a day) was so bad that if I went even 30 hours, I would start one of those headaches. I do not like being that addicted to something.
So one weekend I was having a nasty headache already (I'd slept wrong and it was really time for me to get back to chiropractic care) so I chose that weekend to stop coffee.
I did later start drinking tea, but the way the caffeine in the tea I drink, brewed the way I brew it, affects me is much much nicer than the way coffee's caffeine does it.
So after all of that...the addiction. I have a friend who has been trying to give up diet coke for decades. She *needs to* give it up. She had idiopathic hepatitis (there's actually 4 words in what she had but I'm tired so forgive the shorthand for "I don't know why, but your liver is inflammed) from the age of 13, got addicted to diet coke in college, and even while on the transplant list could not give it up. Only times she doesn't have it is when she's been in the hospital and they won't give it to her. She's now over a year past the transplant (almost 25 years to the day from when she was diagnosed) and still drinks the nasty stuff. Aspartame is HARD to kick. She had nutritionist appointments, doctor appointments, scads of appts every week for years and years, everyone telling her to stop drinking that junk, and she Can Not Stop.
Just be aware that the artificial stuff might cause a stronger addiction than if you'd been drinking the caloric stuff...