HELP ME

Dear Martha,

I am in a big trouble. 😿 My friend invited me to a party for the Saturday at 

midnight but on Sunday a I am going to have an important exam and when I ask my

mom to go to the party, she told me that I couldn't go because I need to study for the exam and go to bed early. If i wouldn't go to the party, my friend is going to get angry with me because many times i didn't accept him to go out by studies and it is the tenth time.

What can I do? I want to have a good exam but i don't want to lose a friend 

HELP ME PLEASE

See ya,

Zeus