In the Jewish cycle of life there are many designated times for 'Simcha', when the emphasis is celebration and revealed happiness. These include the Chagim (festivals) and milestones such as birth, bar/bat mitzvah and weddings.
Interestingly, all Jewish experiences of joy seem to be preceded by serious or solemn moments that motivate reflection, introspection and feelings of repentance. A bar mitzvah is preceded by a program of study; a wedding reception by a Chuppah (a solemn ceremony). Sukkot and Simchat Torah (the most joyous festivals) are preceded by Yom Kippur (fasting and prayer), and Purim (the happiest day of the Jewish Calendar) comes the day after the fast of Esther.
The reason for this phenomenon has to do with the definition of true joy. Happiness is not defined by celebration or any other external stimulus, such as pleasure or wealth. Many people party and celebrate in pubs and other clubs and are miserable individuals. Some even have real reasons to celebrate but seem to remain unhappy.
Real happiness is a deep feeling that comes from within the person's soul. To be happy means to have a sense of purpose, fulfillment and achievement. It comes with the mindset of giving meaning to every experience. Happiness comes with clarity of direction and life's goals and is an expression of inner peace.
Only when there is a foundation of true inner joy, can celebration then play the critical role of nurturing, developing and expressing those feelings of happiness. When the happiness is real then the party can add fuel, vibrancy and permanence to the Simcha.
This is why Jewish celebrations are always preceded by a time of reflection and seriousness. The lead up time helps us focus on the meaning of true inner happiness. Once that is in place, we can throw ourselves into the celebration, expressing our joy to the fullest.