In days of old, there was a person in every town who would light the street lamps with a light he carried at the end of a long pole. There are lamps in forsaken places, in deserts, or at sea. There must be someone to light even those lamps, so that they may fulfill their purpose and light up the paths of others. A chasid is one who puts his personal affairs aside, and sets out to light up the souls of Jews with the light of Torah and mitzvot.
Jewish souls are ready and waiting to be kindled.
There must be someone who will forgo his own comforts and conveniences, and reach out to light those lamps. This is the function of true Chabad Chasid. The message is obvious. I will only add that this function is not really limited to Chasidim, it is rather the function of every Jew. Divine Providence brings Jews to the most unexpected, remote places, so that they may carry out this purpose of lighting up the world.