Some of the comments in this thread show a lack of understanding of how stress and a lack of sleep can effect normal people like you. You don't have to have a permanent mental illness to have an episode like this, it can happen to anyone.
I worked with someone for several years who appeared very much in control of their lives and was an outstanding employee. Then one day someone said something relatively harmless and their world fell in. It turned out that they had more going on in their lives then we knew about. A sympathetic employer, a bit of counselling and a break from work and they were back to normal again.
The professionals were keen to point out that the person was no more prone to a recurrence than any other employee. They pointed out that if employers fire people that have such an event then others are less likely to seek help when they find themselves in a similar situation.