I am in low spirits today. I had a good night's sleep last night. I had regular meals today. But I am sort of depressed, and suffering from what can be called fatigue out of nowhere. When I tried to explain this feeling, this phrase, the fatigue out of nowhere, came spontaneously to my mind. The spontaniety drove me to search for the phrase. There are several examples of it found on the Internet. Yes, this feeling cannot be phrased otherwise than this. I felt sleepy during the day, and made a mistake, a fatal mistake on the job. How can I get myself rid of this?