It's my own fault. Spend too long thinking about stuff from my past that upsets me. But then - is that a cause (or at least an exacerbating factor), or a symptom? Either way, nearly broke down in tears in car on way to work this morning.
Anyway, should get back to work. Might try listening to some comedy. That normally cheers me up. Although today, even Erasure isn't working. :o/