The Queen has praised the "army of volunteers" at the Diamond Jubilee and the Olympic and Paralympic Games.
In her Christmas message, she said it was striking to see the "friendship" of so many people who marked her Jubilee, particularly during the river pageant.
She said the 1,000-vessel pageant on the Thames - on a wet, cold June day - showed a "determination to celebrate triumphing over the elements".
She earlier attended Christmas service at St Mary Magdalene Church in Norfolk.
Her husband, sons and daughter, plus many grandchildren, accompanied the Queen to church. Afterwards she received bouquets of flowers and spoke to about 70 children who had waited outside for her.
The Queen traditionally spends the festive period with her family at Sandringham, but this year has not been joined by the Duke and Duchess of Cambridge, who are with the duchess's family in Bucklebury, Berkshire.
Earlier this month, it was announced that Prince William and Catherine were expecting their first child, after the duchess was admitted to hospital with acute morning sickness.
Prince Harry is absent from the celebrations, as he is currently serving as an Apache helicopter pilot with the Army Air Corps in Afghanistan.
The Queen's message, broadcast in 3D for the first time, was interspersed with footage from the large-scale UK events of 2012.
"This past year has been one of great celebration for many. The enthusiasm which greeted the Diamond Jubilee was, of course, especially memorable for me and my family. It was humbling that so many chose to mark the anniversary of a duty which passed to me 60 years ago.
"People of all ages took the trouble to take part in various ways and in many nations. But perhaps most striking of all was to witness the strength of fellowship and friendship among those who had gathered together on these occasions."
She praised the large contingent of volunteers who adopted many roles during the Olympic and Paralympic Games, held in London during summer.
"We were reminded too that the success of these great festivals depended to an enormous degree on the dedication and effort of an army of volunteers.
"Those public-spirited people came forward in the great tradition of all those who devote themselves to keeping other safe, supported and comforted."
One of the large set-pieces of the year was the 1,000-vessel river pageant, which was watched by an estimated one million people along the banks of the Thames.
The Queen, her husband Prince Philip, and other members of the Royal Family, sailed down the Thames during the pageant and then moored for hours in the rain to watch the vessels sail past. Prince Philip subsequently spent five nights in hospital with a bladder infection.
The Queen said: "On the barges and the bridges and the banks of the river, there were people who had taken their places to cheer through the mist, undaunted by the rain. That day was a tremendous sense of common determination to celebrate triumphing over the elements."
She said that for many - particularly the Armed Forces, emergency services and hospital workers - Christmas was a time for serving others, and being away from loved ones.
"And those who have lost loved ones may find this day especially full of memories. That's why it's important at this time of year to reach out beyond our familiar relationships to think of those who are on their own."
She recalled the Christmas story of the birth of Jesus, saying: "It is my prayer this Christmas Day that his example and teaching will continue to bring people together, to give the best of themselves in the service of others."