I agree. See Richard Wiseman's "The Luck Factor", Skeptical Inquirer (May/June, 2003). Wiseman is a public psychologist, paranormal investigator and author of 59 Seconds (free copy; Anki deck), arguably the best scientific self-help book out there.
EDIT: I just saw that Trevor_Blake had already posted a link to Wiseman's paper on luck.
Is there any rationalist equivalent of "good luck"? I've tried a few variants, such as "work well", "knock them dead", "we're with you" and certain situation-specific phrasings, but haven't found anything that worked generally - though a hearty "may all the gods of Olympus be with you!" can serve. Not a vitally important point, but it would be nice to have something similarly supportive and yet accurate to say.