mad today, glad tomorrow
You're mad today because someone did something dumb, but tomorrow you'll be glad because you'll be too busy doing something even dumber.
My brother broke my favorite toy. I'm mad now. But tomorrow I'll be glad because I'll be too busy breaking his favorite toy.
My dad forgot my birthday. I'm mad now. But tomorrow I'll be glad because I'll be too busy forgetting his birthday.
My dog ate my homework. I'm mad now. But tomorrow I'll be glad because I'll be too busy eating my dog.