depend on the kind on information, if it's very personal then i would be emotional, have a hard time mentaly and would probably get proper institutions involved, but if it's not very importnt information, then i would try to know the reason, how it happened and thy to fix my security issues
I would search for the cause of leaked info and improve security around that system area
I would contact police or other authorities
Be sad i guess? Bad question lol.
depends what information! ranges from being kinda sad to fleeing the country
install security programs
Well if it's not my bank acount I would not care, because I don't put personal information that could damage my image on internet