@redweasel  
oh interesting! I think the drowsiness is just in the imagination…  
I’m drinking fair-trade coffee right now, it smells the best out of all coffee!

caffeine blocks adenosine receptors, which upregulate (produce more of them) the longer they aren’t going off, so when it wears off you get drowsier easier (but not more drowsy). it also makes your blood vessels dilate easier (which makes getting headaches easier).
 
about 2 days for the receptors to downregulate, though people on high doses of caffeine can have negative effects for up to 2 months. since coffee stops the negative effects, it’s best to wean yourself slowly to a moderate dose.
 
as someone who can’t handle caffeine, I’ll say most “addiction” isn’t caffeine at all, but social stigma against being sleepy, having to compete with all the other coffee drinkers.
 
best way to avoid upregulation (and tolerance) is to avoid drinking coffee for long periods of time, only using small doses when you need an hour of alertness, but can crash afterwards. also don’t believe the lies that more coffee will keep you more awake. any more than 10oz (brewed) (depending on your brain weight) will have little to no beneficial effect.
 
also try to use synthetic caffeine, or at least fair trade coffee. it’s never a good idea to buy stuff from (literal) slavers, no matter how good it smells.