Washington (CNN) - Janet Napolitano has a few words of advice for whoever succeeds her as secretary of the Department of Homeland Security: "You will need a large bottle of Advil."
Napolitano said Tuesday her job is "very big and complex" but is also very rewarding.
Napolitano will leave her post at the end of next week to take over as head of the University of California system. Her portfolio at DHS is perhaps the broadest of any Obama administration cabinet member and includes working to prevent terrorism, responding to natural disasters like hurricanes and tornadoes and providing security at the nation's borders.
In a farewell speech Tuesday, Napolitano defended the performance of her department but said there is no way to prevent every crisis.
"We may not be able to stop all threats all the time, but we can - and must - be prepared to address them quickly when they happen, minimize their consequences, draw pragmatic lessons, and emerge stronger and better," Napolitano said.
She pointed to the Boston Marathon bombings. While the attacks were not averted, Napolitano said DHS provided grants and supported exercises that helped the city of Boston respond well to the mass casualty event.
"The well-timed and coordinated emergency response that immediately followed the marathon attack was no accident," said Napolitano. "It was the product of years of planning, training, and investment in building state and local capacity."
Four people were killed and more than 200 were injured in the April bombings.
Napolitano also defended the government's 2012 response to Superstorm Sandy. Napolitano said the DHS response was to "lean forward in our preparations, surge assets and people into the disaster zones as soon as possible, streamline assistance to the victims and cut red tape, and find solutions to problems as they arose."
Not everyone was satisfied with the DHS response to Sandy which killed more than 70 people and damaged or destroyed more than 650,000 homes.
Napolitano is leaving DHS as a comprehensive immigration reform bill that passed the Senate faces an uncertain future in the House. A former governor of Arizona with extensive knowledge about immigration, Napolitano has been one of the leading advocates for immigration reform.
Obama has yet to announce a nominee to replace Napolitano. CNN reported earlier this month that Boston Police Commissioner Ed Davis is on the short list of candidates to succeed her. A Boston government official told CNN Davis was going through the vetting process for possible selection. Davis received accolades for his department's response to the Boston Marathon bombings and the manhunt for the suspects.
The source also said William Bratton is also on the short list to take over at DHS. Bratton, now in the private sector, once headed up the police departments in New York, Los Angeles, and Boston.
Several people currently serving in government also may be under consideration, according to various media reports. Those include Craig Fugate, who leads the Federal Emergency Management Agency and John Pistole, the head of the Transportation Security Administration and the former number two official at the FBI.
Ray Kelly, the current commissioner of the New York Police Department, is another name often mentioned. His supporters included Sen. Chuck Schumer, D-New York.
Thad Allen, a retired admiral who led the Coast Guard, could be in the running. Allen also was the national incident commander charged with leading the response to the Deepwater Horizon oil spill.
Former Connecticut Sen. Joe Lieberman has also been mentioned in media reports. He was the chairman of the Senate Homeland Security Committee. Maine Sen. Susan Collins, the former top Republican on that committee, also has been mentioned.
CNN's Darius Walker contributed to this report.