Never give up on a dream just because of the time it will take to accomplish it. -Quote

This is one of the quotes that cover the theme of ideas VS execution. As most of the business people are split on either side of the debate. Many, and especially from the tech startups side consider dreams or ideas worthless unless executed (startup execution being not easy). Others, and mostly from the traditional business side, consider that dreams and ideas are important, and that they have a big role in success.
Related:
The true entrepreneur is a doer, not a dreamer.
Ideas are worthless. Execution is everything.
There’s no shortage of remarkable ideas, what’s missing is the will to execute them.
You have to believe it before you see it.
Imagination is everything. It is the preview of life’s coming attractions. – Albert Einstein

Never give up on a dream just because of the time it will take to accomplish it.

– Unknown quote

Back to the quote itself, it is straightforward, never give up your dreams, no matter how long they take.
From my point of view, i see this statement from 2 perspectives:
– Without a dream, or goal, you will end up disappointed in yourself when older, but also you would probably be less successful than you hope to be.
– But if you have a couple dreams, and one of them is difficult to achieve, and data is clear that there is a low chance/possibility to make it happen, i think it is ok to give up on some dreams in favor of focusing on other with more potential of success.