Love them or loathe them, there is no doubt that being the leader of a country is more high pressure than the vast majority of jobs.
And with every politician sure they can make a difference to the nation they serve, many of them begin their terms in the White House, the Beehive or Downing Street, fresh faced and full of youthful enthusiasm.
But after a decade running a country, the stress of doing so can sure start to take its toll.
In December, Prime Minister of New Zealand John Key announced he would step down from his position as he had nothing more to give the country. We took a look at how he's changed since a forty-something leader in 2008, and how other world leaders fared over their terms of office.
Click through for John Key's thank you to New Zealand.