I continually cycle on/off caffeine when needed. I can usually drink about one coffee/day and the positive effects will last about a month (hyper-focused, etc). After this, it no longer works. If I drink more than this, I start getting anxiety and have a hard time working and sometimes even going out to meet people.

So, I usually stop completely for a few weeks. This results in headaches, pains in my legs and sometimes arms for about a week.

After a few weeks, I can start again and the positive effects will continue.

When I was in high school, I didn't think about my caffeine intake and would regularly drink a 2-litre of mountain dew/day. I never understood why I had tons of anxiety....

I am one of the people who can experience painful withdrawal effects: upon significant disturbance of coffee intake amount(less)/time after a few days at 3/4 espressos a day, I would experience a painfull and incapacitating headache in the following 12 to 24 hours.

I tested it, yep, was coffee (did not test with another source of caffeine though). Had 100% "success" over a few tests.

It is vicious: I don't need to "stop" drinking coffee to experience the headache, just need to disturb significantly the amount(less)/time of intake.