The only thing which has no restrictions on it, which is completely free and you don't need to reach a certain age limit to have it, Dreams !
No one can stop you from dreaming and interestingly no one can force you to do so either. Dreams have been the reason behind marvelous inventions and discoveries and at the same time, they've served as a point of inception for huge destruction. Its a very interesting fact, a person's perception depends upon his ability to dream. If he dreams big, he is definitely an optimist. And if he's scared of his dreams being shattered, he's a pessimist.
'Dreams Do Come True', only if a person has that required level of zeal, enthusiasm and sincerity to make it come true. Nothing can throw hurdles on his way to success then. Nature designs his way and no other force is great enough to hamper the force of nature. There is no way he'll be unsuccessful then.
The intensity of dreaming depends upon a person's creativity and perception. If one has an impression that something is impossible to be done, it really would be impossible but only for 'HIM'. But if someone is determined to do the impossible, nothing can stop him then. Of course criticism might hamper his determination initially but this criticism can make his sincerity toward his goal even stronger. Such is the magic of constructive criticism.
Surprisingly this dream-big thing has been working quite fine for me. So go ahead and start dreaming !
Oh yes, you can even go and steal the moon (Despicable Me). Its all about dreaming big. Cheers !