Day in bed

I rarely do this, but yesterday I slept most of the day, waking at 4.45pm-ish then after a bath, and struggling to keep my eyes open, went back to bed before 9pm, and then slept the clock around until 9am this morning. I feel like I have the aftermath of a cold. When I took my peak flow yesterday it was below the 75% marker the respiratory nurse showed me to put on, yet today, apart from a slight sore throat and slightly achy ears, I feel OK.
And, this morning I felt very awake, so obviously I needed the sleep.