I don't believe for a second that all dreams are possible in a practical sense. Example: Let's say that I, a rowdy Montana cowboy by nature, had decided from birth that my greatest dream was to be crowned Miss America. Yeah. Right. Dream on, cowboy.
I DO believe that MOST dreams are possible when you work for them...the most important question being: Are you willing to pay the price? Example: As a young child, I dreamed of becoming World Champion Saddle Bronc Rider. Then, at the age of 19 (and with a few years of actual rodeo experience), I reevaluated both my native talent and the price I was willing to pay.
As a result, I downgraded the dream to making the National Finals in Bull Riding by the age of 24. That WAS more in line with my genetic abilities, but at the age of 22, the PRICE slapped me upside the head...and I quit rodeo entirely, just at the point where my peers knew I could ride a pretty fair bull.
Summary: Work is part of the price tag for realizing any dream, but far from the only price. If you're willing to "Always Pay Full Retail" for the dream, then yes, in MOST cases the dream will turn out to be possible.