u/nightfern

 Iam going to throw this out there.  I never say "Good Luck" to someone, when they are about to take on a semi-serious endevour.  I like to say "Good Skill".  
I feel in the moment when you can give someone something to take with them into the fray, then why say something that is real, and not "just a saying",  why not say something to highlight them and their "Skills".  
So for example, I used to be in "Information Technology".  When I was about to do an upgrade or install something new, my boss would say "good luck".  Now being someone with anxiety I wanted something from them to help overcome the anxiety.  Unfortunatley and it's not their fault, I feel like needing Luck to do the upgrade is not something I want to consider.  I want to be told that my skills are more important then a pull of a slot machine handle.

"Good Luck" in a saracastic moment is fine, I think its more ment for that type of use. Basically if you are going to tell someone a saying in an important moment then don't be scared to say "something real".