Yeah I've had days like that. It is usually due to sleep-deprivation, stress, hormones (PMS) or a combination. If it is possible, I usually have a nap, or lay down for an hour or two just to breathe deeply and cry if necessary.
If that's not possible, I usually use one of my breaks during work and just lock myself in the bathroom stall with a piece of paper and I write down everything that is bothering me. I might bribe myself with chips or something for later in the day so I have something to look forward to as well.
If my day is going truly horribly, I'll call my boyfriend and he helps me calm down.
It's not in what you say, it's in what you do (Oasis)
Feeling bored? Why don't you wander over to my blog sometime. http://thebohemiankitchen.wordpress.com