When I say "good luck", it usually means "You have no chance of succeeding and I am hoping my obvious sarcasm will quell your stupidity."

Nobody really means it because luck is a non-transferable, non-existant sort of "God". You know, we kiss his idols and tote them around for good measure but they never work because the "God" isn't really. It's like someone saying "Happy Trails Jesus!"

So possibly, when someone is telling you "Good Luck", they mean "PG, you suck and won't succeed." So maybe you should take it literally.

Like if you're going into surgery.