Never let anyone piss on your dream. Avoid all that weakens you... and that may even include some family and friends. Real friends will support your dream. I've never heard a super successful champion tell me or tell anyone "it can't be done... you can't do it." But underachievers say it all the time. Only those who never did something, say it can't be done. THEY HAVE NO CREDIBILITY!
Dream big.
Dream often.
Act on those dreams daily.