Why is this and how to control it?

So it’s like I don’t feel mad, sad, happy, or tired. But yet I feel down for some odd reason. Like, at the time of this post, I have work at 3 hours. But I don’t feel like I have the energy or mental energy to get through this workday. Like I feel sad but I’m not sad. Does anyone know what I’m talking about or how to get out of this feeling?
Why is this and how to control it?
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