Such a celebration in also connected to the fact that on his 13th birthday a boy enters the age of maturity and is responsible to observe the 613 mitzvos.

The same is true of a girl on her 12th birthday.

Since every Jew has the "presumption of righteousness" the assumption is that this young boy or girl will certainly grow up to fulfill the dictates of the Torah. Consequently, there is reason to rejoice at the time he or she accepts the yoke of mitzvos.

For this reason men and women above Bar/Bas Mitzvah should see in their birthdays additional significance:

1. It is the anniversary of physical birth,

2. it is the anniversary of maturity, or Spiritual birth.

As the Shulchan Aruch explains:

The consummate indwelling of the holy soul in a person takes place on the 13th birthday [lit: 13 years and a day] for a male and the 12th birthday for a female. For this reason they become responsible by Biblical law to fulfill the mitzvos of the Torah. (Shulchan Aruch Harav end ch. 4)

With this in mind, whether you are 13, 30 or 83 you have a reason to celebrate your birthday. And at each age you can find satisfaction and growth when you become one year older.