Dreaming/dreaming big is advisable and encouraging too. But mind you, in order to make your dream a reality. You must/have to pull your weight i.e. endeavour to do what you ought to do and when you ought to do it. Because doing just that, will speedily metamorphose your dreams into realities.
Everything you will ever need to go after/accomplish/fulfill your goal/dream/vision or any other target/aspiration which you will ever set/aspire for is already sitting/waiting patiently inside you. Oh! Yes, all you've got to do is just to take a leap/step of faith forward/towards your goal/target/dream/vision/aspiration and then, sit back and watch it materialize/come true gradually/sooner or later.
History has proven, God has never given anyone a dream Without also including the power to achieve that dream It is up to us to claim the power and go after that dream, Or just claim , it was only a dream.