Society prescribes what you "must" and "must not" do in many ways: schools, companies, social groups, etc. It also indoctrinates that your opinion, dreams, ambitions, and hopes don't matter.
As I've stated before, posing problems is at a higher level of creativity than merely solving problems posed by others. Cars, aeroplanes, computers, although based on scientific principles, look and work the way they do because of someone's opinion.
When all's said and done, every idea, gadget, machine, is just an opinion that got popular. And a popular opinion doesn't make your opinion worthless. So never disregard your dreams.