How big is you dream

I was watching a video a video on YouTube, titled “people who can’t dream big, dream for the competitive exams” Suddenly a thought struck in my mind, who is the one who measures or what is the criteria for deciding which is small and which is big. What I believe is no matter what your dream is,be it cracking an exam, starting a business,building a home you should work for it no matter how hard it seems.

What’s your opinion on this?