Such an occasion seems a fitting time to not only take stock of the past 10 years, but to look forward.
Being leader of both the party and the country has been an incredible experience.
Along with my Cabinet and caucus colleagues, we steered the country through the global financial crisis which was arguably the worst recession since the Great Depression.
We have stood with Christchurch in the wake of the earthquakes - the greatest natural disaster to hit our country since 1931, and we have mourned the victims of the Pike River Mine disaster; one of the saddest days our small nation has endured in recent times.
During my time as Prime Minister the Government has positioned New Zealand so that our economy could harness the opportunities offered by a burgeoning Asia and a more connected world.
Reforms have been far reaching, including substantial changes to our tax, welfare, planning and labour laws, not to mention the successful partial sell-down of state companies, the considerable overhaul of our Justice, Security and Corrections agencies and, of course, trade liberalisation.
Ten years since I first became leader of the National Party, I believe we can look back on advanced race relations and real momentum in the Treaty settlement programme.
We also have a more confident, outward-looking and multi-cultural New Zealand that competes and succeeds on the world stage.
Throughout these years I have given everything I could to this job that I cherish, and this country that I love. All of this has come at quite some sacrifice for the people who are dearest to me - my family.
For my wife Bronagh, there have been many nights and weekends spent alone, many occasions that were important to her that I simply could not attend.
My daughter Stephie and my son Max have transitioned from teenagers to young adults while coping with an extraordinary level of intrusion and pressure because of their father’s job.
I thank them for their tolerance. Bronagh and I are immensely proud of them.
My family has also had remarkable opportunities and experiences as we have met people and visited places from one end of our country to the other.
We have celebrated alongside fellow Kiwis in their happiest times, and wept with them in their saddest.
Simply put, it has, for me, been the most remarkable, satisfying and exciting time of my life.
But despite the amazing career I have had in politics, I have never seen myself as a career politician. I have certainly never wanted my success in politics to be measured by how long I spent in Parliament.
The National Party is in great shape. Bill English has told me that in all his years here, ours is the most cohesive Cabinet he has seen. And I personally am humbled and gratified that after eight years as Prime Minister, my personal support from the public remains high.
I absolutely believe we can win the next election.
But I do not believe that, if you asked me if I was committed to serving out a fourth term, that I could look the public in the eye and say yes.
And more than anything else in my time here, I have tried to be straight and true with New Zealanders.
I also believe that leadership change, for the right reasons and handled well, is good for a political party.
For all these reasons, I today told my Cabinet and caucus colleagues of my decision to step down as Leader of the National Party and as Prime Minister.
It is my expectation that on Monday 12 December National MPs will hold a special caucus meeting to select a new leader and later that day I will tender my resignation to the Governor-General.
This has been the hardest decision I have ever made and I do not know what I will do next.
But for me this feels the right time to go.
It gives the Cabinet and caucus plenty of time to settle in with a new leader before heading into the next election with a proud record of strong economic management, a commitment to the most vulnerable in our society and lots of ideas to keep lifting New Zealanders up in the world.
It would be easy to say I have made this decision solely to rediscover the personal and family life I once had, and that is a factor, but it is one among many.
Over the years I have observed many leaders who, in a similar position, fail to take this step.
I can understand why. It is a hard job to leave.
But, for me and the National Party, this is a good time to go. Party membership is high and the party is well-funded. The caucus is talented and eager to serve, and one of the achievements of which I am proud is having built with my colleagues a Cabinet team that is capable, committed and cohesive.
That is a great legacy for National’s next leader.
Just as I grasped the challenge of leadership so will a new leader.
Inevitably they will bring their own personality, emphasis and priorities to the role.
This is part of the process that allows a long-serving government to keep delivering.
For my part I am confident the caucus has a number of individuals who would make a fine future PM.
It is inevitable I will be asked who I will vote for at the caucus meeting on December 12.
Whoever the caucus elects will have my unwavering support, but if Bill English puts his name forward then I will vote for him.
For 10 years now Bill and I have worked as a team. I have witnessed first-hand his leadership style, his capacity for work, his grasp of the economy, his commitment to change and, most of all, his decency as a husband, as a father, as a friend, a colleague and as a politician.
Bill has, I believe, grown a great deal since he was last Party leader.
Fifteen years on he has more experience and the party and political cycles are quite different.
I believe that National, under Bill’s leadership, would win the election in 2017.
This is not the time to thank all of those who have made the past 10 years possible for me.
But nor can I stand here without acknowledging Bronagh, Stephie and Max who have sacrificed a lot for me to have been able to do what the job demands.
No person in this role can succeed without the support of an enormous number of talented and dedicated individuals.
I thank my deputy Bill English, the Cabinet and caucus for their loyalty and energy and, of course, my wonderful staff, so well led by Wayne Eagleson, who have done more than I ever could have hoped or expected.
I also wish to thank and acknowledge our support partners ACT, United Future and the Maori Party without whom the strong and stable Government we have delivered would not have been possible.
I have no doubt my successor will look to build upon these relationships.
Last but not least, I wish to put on record my everlasting gratitude to the people of Helensville for electing me, and to the New Zealand public for their support, faith and encouragement. It has been my privilege to serve you all.
I have always believed that the test of a good Prime Minister is that he or she leaves the country in better shape than they found it. Over time, others will judge whether I have done that.
All I can say is that I gave it everything I had.
I have left nothing in the tank.
Finally, while I intend to stay in Parliament long enough to avoid the cost and inconvenience a by-election would cause the good people of Helensville, I will at an appropriate time prior to the next election step down as an MP.
On that day, I shall walk from these buildings for the last time, a richer person for the experience and privilege of being here, and hoping and believing that New Zealand has been well served by the Government I led.