Win or lose, many candidates' faces showed signs of exhaustion on election night.

Political campaigns require endless energy — and a thick skin to deal with personal attacks. And of course half the candidates have to deal with the disappointment of losing.

So, what's the psychological impact of running for office, and what's a candidate's emotional state at the end of a grueling campaign?

Philadelphia businessman Sam Katz says running for office brought out a new side of him.

"I look at the campaigns of Sam Katz as 'who is that guy where did he come from' because that guy and this guy, today, seem to be very different people."

Katz ran three times for mayor of Philadelphia and once for governor of Pennsylvania. He says his 2003 campaign took a huge emotional toll on him. He recalls a night when hecklers drowned out his speech during a rally. He says after weeks of being heckled at campaign events, and seeing the same group of hecklers intimidate his wife and children, he snapped.

"I was out of control furious, I had to be dragged into the car, cause I wanted a piece of everybody, I was so angry, I don't think I realized how beat up I was in that process, until it was over."

Personal attacks are especially hurtful because many candidates run out of a sense of duty, says New York psychologist Lisa Cohen.

"Part of your identity is that you want to be a nice person, you want to help, and yet you get accused of all sorts of heinous things that never occurred to you before, and if you have a family, of course they are exposed to that."

Cohen says candidates need resilience and a very strong support system to cope.

Many candidates admit losing is painful, and can lead to a sense of failure and depression.

British psychologist Ashley Weinberg warns winning could be even worse for your mental health.

"Levels of psychological strain seem to be higher six months after they have begun the job for the first time than it was in the months leading up to it, when they were in middle of their campaigning."