came and left suddenly

today I had a bit of an odd experience, while I've been in a mostly lower period of my depression, it's been a fairly mild one overall, but this morning, I seemed to be slipping into a pretty bad one, all the normal thoughts and urges of my worst depression spikes were rearing up, I did my best to try and focus on the book I was trying to finish before the new year, and a few hours later I was starting to normal out to how I've been recently.  I'm not sure how to take the experience, based on my feelings, and the general way it felt it seemed more like a depression spike then when I get sad, but i've never had a depression episode that was so short.