You know, Mat, what seem like sudden mood swings can often be caused by a THOUGHT. It can be so deep that you're not even aware it's happening, but if you are alert you may catch something that you're saying to yourself which results in a sudden crash.

With me it can sometimes be something as seemingly trivial as "Omigod, what in the world am I going to do with the rest of the day?" And then I start to get scared and down.