Why I Gave Up Coffee Yesterday
Yesterday, I did not have my usual afternoon coffee.
Two days ago, I had decided to give up coffee (for at least two or three weeks). My final cup of espresso made at work:

I found a surprising variety of reasons to quit coffee.
Prelude: my history of coffee drinking
I was not always a coffee drinker. I almost never drank coffee in my life until less than a year ago, in July 2011, by accident when someone at work found a discarded cheap espresso machine in the hallway and we managed to get it working. It did not produce anything resembling real espresso, apparently, but it worked to make coffee that was better than the standard drip coffee that I always found disgusting (one reason I was never a coffee drinker).
The old “espresso” machine leaked water, however, so my boss bought a new machine that was far better, although still low end (about $150). This functioned well enough that I decided to start buying coffee beans and grinding them and making one small cup of espresso for myself each day at work.
I set a policy of only having this one cup on weekdays and being coffee-free at home on weekends.
A general reason: to change my routine
Sometimes I like to change my routine for no particular reason other than change. From experience, I have learned that often, changing something for no reason at all can be beneficial. I then wait to be surprised by what I learn, what I observe, and I always have the option of noting that the change was for the worse and therefore returning to my routine.
I’ve done these kinds of changes when it comes to my exercise routines, my music practice, my use of computer programming languages and tools, etc. Through experimentation, I improve my routines and keep my mind and body fresh.
Decreased appreciation
After months of regularly making espresso at work, I realized suddenly that it had become a mindless habit I “depended” on, rather than a special treat that I savored for itself. I used to take a few minutes away from the computer at work to enjoy my espresso, but apparently at some point I just started sipping it absent-mindedly while continuing to do work.
It seems a waste to do something mindlessly that I might as well not do at all. Even worse, had I become caffeine-dependent or something?
Health concerns
It was not clear to me whether my mild coffee habit has real benefits or drawbacks, but I have been worrying about possible drawbacks.
I do know that when I have too much coffee, I get “wired” and that does not help my mental or physical state. So the question is, have I been getting “wired” and not realizing it all these months?
Sometimes I get headaches, and wonder whether coffee is increasing my blood pressure.
Also, there is the matter of coffee being acidic and possibly nutrient-leaching.
In addition, I’ve been having some problems keeping weight on. Coffee seems to make me lose weight. I already weigh less than I did 24 years ago in college. I don’t need to lose weight. My body goal is to gain strength and flexibility and muscle mass, not lose weight.
Finally, how does my afternoon coffee affect my sleep quality?
Observations after one day
Yesterday at my “usual” coffee time, I noticed a feeling of lack as I bypassed my usual cup. Perhaps I really did become dependent on coffee as a way to boost my alertness in the afternoon.
Also, I got sleepier and earlier last night. Again, was the day simply unusual for me, or has it been the case that coffee has artificially interfered with my “natural” body signals to go to sleep?
Conclusion
I am quitting coffee as an experiment to see what happens as a result. I hope to learn something about how dependent I have become on it (psychologically or physically), and monitor changes in my health. I am by no means arbitrarily giving up coffee forever. I expect that two or three weeks will be enough for me to learn something useful. Then I can choose whether to reintroduce coffee into my life, and at what level. Certainly I cannot imagine any harm from drinking a cup every week, but the 5-day-a-week habit has raised suspicions.

My experience with quitting coffee is that the withdrawal effects only last for a few days. Lately I've reduced my coffe consumption a lot because I have a large stock of interesting teas to drink instead. Unfortunately, my total caffeine intake is as high as ever. It's actually easier to overdue it with tea because tea is so pleasant to drink. Coffee is more self-limiting: after a few cups I am sated.
Tea is very different for me than coffee. Caffeine's not the only active ingredient in these beverages. That said, I will also stay off caffeine generally for a while.
My last cup of coffee was a little over a month ago. But since I've been a regular coffee drinker my whole life, the experience might be a bit different. (I have a memory involving coffee from when I was 12 years old, by high school coffee shops were ingrained in my social life, I was regularly dependent on caffeine for staying awake in college, and I first started to notice impairment from caffeine withdrawal when I was about 22.)
Unfortunately, it turns out I'm not capable of moderating my caffeine consumption without slipping back into old habits and then going overboard pretty quickly. So, no coffee or tea at all.
I drink maybe 4 or 5 cups of coffee a day and have for years. I wish it would help me loose weight but nope. It does help keep me 'regular'. But weight gain has been the opposite problem for me - and I doubt coffee has anything to do with it. As for being wired. I Admit I LIKE being wired, its my preferred state. Well that next to the opposite - being subdued. Although I dont like the shaky dizzy part of too much so 5 is my limit. As for health ... like eggs and sugar and wine and a million other things every few hears the pendulum swings and last I heard coffee was good for you but maybe next year it will be bad.
The best part of your story is that you were doing things out of a habit instead of enjoying it. Good for you. I do believe one should enjoy ones vices so if you don't enjoy it give it up to make room for another vice you do enjoy.
Amusingly, I'm sort of back to coffee now, after basically a two-month absence (with two exceptions while away from home, both of which left me in an unpleasant state). I made espresso at the office on Monday, and I did it today also. I think as long as I just have a little cup twice a week (and out of enjoyment rather than habit or an attempt to artificially stay awake instead of sleep more), it will remain a special treat.