I can't believe I overslept

[xt1me]

I had stayed up too late last night but not that late.

My alarm went off too early because I had forgot to change it so I figured I could have another few hours sleep and reset it and went back to bed. Either I set it wrong or I slept though the second alarm because next thing I know it was half one. I had a dentist appointment at 12! It was kind of embarrassing.

I rescheduled my appointment with out any difficulty but I threw me off for the whole day.

Why did I sleep so late?