I really try to be cheerful at work but can easily be brought down by others moods, particularly "down" moods, but I think that's because I've a personal battle with depression.

One of the major causes of black moods here is out of the building for a while and the atmosphere is very different at the moment, peaceful and serene almost.  I even heard birds chirping earlier

I'm hoping, as Jodith mentioned earlier, that my hysterectomy in the summer will be a major turning point in mood for me.