Way back when I was younger I had alarm set on my phone for 9:30pm.
It was my bed time alarm.
It turns out Apple decided that more people would like a similar feature.
Unfortunately I’m not always good at following it.
But I do find if I stick to a rhythm of a similar (early-ish) bedtime and a similar wake up time that life is generally better. If I hit the sack after midnight, the next day I am Mr Grumpy pants.