Lacunae

I'm in the midst of a lacuna - and no, that's not a make of car. Having finished doing my Diploma in Teaching in the lifelong learning sector (DTLLS) and my Level 5 ESOL Specialist Qualification, and currently waiting for the results, I feel at something of a loose end. Even though I'm still busy at work and have plenty to do, I can't help but feel that I'm not doing enough, and I don't seem to have any interest in anything. hence the reason I feel that this is a lacuna - a break between things, a pause between actions.
In fact, it would be easy to say that my life is one long story of frenetic bursts of activity followed by lengthy periods of torpor, longeurs if you will (they're certainly not shorteurs). For some reason, once any given period of intense activity ends, I find it immensely difficult to become engaged with something new, or the next phase of a project. I'm damned if I know why, either: it's not for the sake of my health. One thing that becomes immediately apparent once I finish something is that I become extremely irritable, bad-tempered and generally depressed. My assumption on this is that this is probably a result of an alteration in brain chemistry - I suspect that the stress of an intense work project makes me produce a shedload of endorphins, and once the pressure is off, production subsides, leaving me feeling as I do - withdrawal? If it's the case that I feel so crap after finishing something perhaps it leads me to feel reluctant to move on to the next thing.
What is always worrying is the fact that it takes me so damn long to move on to that next thing. I'm far happier working hard than not - so why these breaks in the action? And, as you can see, it means that I don't write on this thing as often as I would like. Forgive the most recent lacuna.