Mixed is usually " hell on earth " as in on your bathroom floor with a toothbrush bawling your eyes out unable to sleep and in a productive cleaning frenzy (thanks BipolarRn for that long lasting description)

For me if I notice a large lack of sleep I have chronic insomnia , but by day 4-5 I am in a ugly mixed.

It's not abnormal to see a mood fluctuate in a day.

Watching your sleep pattern is the best way to keep an eye on things.