The Overview Effect
Have you read Frank White's book, The Overview Effect?
He talks about the reactions of space travelers to seeing Earth from a distant vantage point. Apparently this is what got Scott Carpenter in trouble on his one and only Mercury spaceflight in 1962: He was so enamored of where he was and what he was seeing that he missed critical items in his flight and ended up splashing down over 200 miles off target.
No dreamers allowed in the manly early Space Age.
http://www.astrobio.net/cgi-bin/h2p.cgi?sid=646&ext=.pdf.
http://www.aiaa.org/store/storeproductdetail.cfm?ID=526