I found that my caffeine consumption was causing a lot of problems relating to sleepiness and mood. It may be that you are experiencing withdrawal symptoms due to a high tolerance to caffeine. You might want to try cutting out all caffeine - not just coffee but tea, fizzy drinks and perhaps even chocolate (although I didn't give this up). This resets your caffeine tolerance levels after a few weeks and you can then reintroduce lower amounts of caffeine slowly, so as to keep tolerance + withdrawal symptoms low. Even light withdrawal symptoms are an unpleasant experience, so you could always slowly reduce instead of going cold turkey.
It could be that you need to get more sleep, however. It might also be the sloth and torpor hindrance/boredom.
"If beings knew, as I know, the results of giving & sharing, they would not eat without having given, nor would the stain of miserliness overcome their minds. Even if it were their last bite, their last mouthful, they would not eat without having shared."