Persisting in Delusion

"It is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring." — Carl Sagan

Is this true? When it comes to the cosmic universe, perhaps. When it comes to our personal universe, is it better to persist in delusion? Isn't that what a dream is, a delusion? The dream might be attainable with luck and hard work, in which case it's not a delusion. If it is not attainable, is it better to hold on to the dream or is it better to depersist in...