I overslept and missed my nephews party and really feel bad about it.
Yesterday was my nephews birthday party. Unfortunately, I missed it!
user
Uhmnn, so how do you  think  she would react? 
assistant
She was very sad. I felt really bad that I overslept and missed it.
user
Anyway  you have to find a way of better explaining  ,hope he'll  understand? 
assistant