Don't you think it's pointless to worry about what will happen tomorrow?

Literal

Tomorrow what [subject-が] occur [question-かと] worry [nominalizer-の] [topic-は] futile thing-is [quotative-と] think-not?

~と心配するのは無駄なことだ — 'worrying about X is a futile thing' — uses の-nominalization to turn 心配する into a topic. と思いませんか invites agreement — 'don't you think?' A layered sentence combining embedded question, nominalization, and a tag question.