Don't know if you're thinking of anything in particular, so here's the overview.....
Coffee stimulates the production of adrenaline above and beyond that naturally produced by the body.
As you might imagine, this is not sustainable in the long term and heavy users need more and more coffee to 'function', just like any other stimulant drug.
We normally advise people to limit themselves to 3 cups (or 3 shots) per day. Either will supply around 200mg caffeine, which is enough to see professional athletes test positive, as it is an ergogenic.
Some people are more sensitive to the effects of caffeine than others and I would suggest that the more nervous/anxious/tense the individual, the less coffee they consume.
Such people produce enough adrenaline already and more is likely to upset their sleep-wake pattern (the circadian rhythm).
Short-term, caffeine can boost performance in endurance sports, aid concentration and, of course, boost energy and feelings of well-being but it also causes a short term rise in blood pressure (so don't have a coffee before seeing the Doctor), anxiety and even palpitations.
It also reduces the absorption of magnesium, ironically essential for helping you relax.
Caffeine takes around 8 hours to metabolise, is the worlds most popular drug and more cups of coffee are drunk daily than there are people on earth.
Calorie content varies from 4-6 calories for black to 530 for a cream, sugar and chocolate laden abomination from a well-known coffee chain.
In short, no, it's rubbish for you but it tastes fantastic.
I've switched to decaf and I don't miss the hit at all.
Please come back with any specific questions.