I am not allowed to sing "The Night Chicago Died" around my friends before going into a desperate battle alone. While it boosts my spirits and calms my nerves, it makes Molly, Michael, Charity, Thomas, Murphy, Elaine, Mouse, Mister, Susan, the Alphas, and the rest sick with worry.
On the other hand, humming it as I walk back in the door after winning said battle is a classy touch...
(Just try to imagine what sort of situation would have Harry walking off into a desperate battle, and all these people are staying behind to wait...that would be very strange.)