what do you do when you are stressted and grounded at the same time?

Read a book, work on books, try to sleep off the grounding

Nothing

Being grounded = freedom

Do whatever the fvck you want! Don't worry about whatever you're stressed over, in the long run it doesn't matter. You'll look back 30 years from now and say "I can't believe I was stressed about that". Enjoy yourself! Enjoy your 'punishment'. If your mom sees you're not upset over your punishment she might end it early, who knows?