The fast of Tammuz is one of four annual fasts commemorating the destruction of Jerusalem by the Babylonians and later by the Romans.
The fast of Tammuz marks the breaching of Jerusalem's fortified walls during the siege and is the start of three weeks of national mourning culminating with the destruction of the Temple on Tisha B'av.
The purpose of these fast days is to allow the messages of these events to impact our lives. Fasting affects our daily lives, stops us from ignoring the issues and forces us to engage with the mood of the day.
The sages write that the fast is a means to an end rather than an end in and of itself. The act of refraining from food and drink ought to motivate us to evaluate our actions, and to think positively and constructively about how each and every one of us can play our part in bringing about the redemption.
