Have group members take the number of years they have lived and divide that number by 4. For example, if a person is 44 years old, he or she would divide that number by 4 to get 11.
Once everyone in the group has their number, pass out pens and paper and have each person chart out his or her life in 4 sections, with each section corresponding to the increment he or she came up with.
Here's an example:
My life
__________________________________________________________
Ages 1-11
Ages 12-22
Ages 23-33
Ages 34-44
Once this is done, ask each person to share with the group which of those times was the happiest in his or her life, and why.