For a human being birth is a joyous time.
It is a time of fulfillment for the parents who were blessed with a son or daughter, for the Jewish people who gained another member, and for the child himself/herself who came into existence.
Therefore, when a person reaches maturity, each year on his/her birthday, it is appropriate to express gratitude to the Holy One, Blessed be He, the Giver of life.
Just as the birthday of a people is celebrated each year with rites and a ritual, so too, the birthday of an individual Jew should be appropriately observed.
An individual's birthday can be utilized to strengthen and increase all aspects of Yiddishkeit, Torah and mitzvos, starting with the three pillars which uphold the world: Torah, prayer and charity.
These good practices should be observed on the birthday and good resolutions for the future should be accepted.
Most importantly, gather your family or friends for a festive gathering (to celebrate the mitzvah) on your birthday and the joyous party will encourage others to accept good resolutions - and the happiness that is generated will imbue your future observance with enthusiasm and zeal.