The Alter Rebbe explains that every Jew possesses a divine soul that is literally 'a part of God above,' and that the divine soul's entire thrust is to return to and cleave to its Source. The struggle of daily life is the story of this soul's longing to run home to God.
פֵּירוּשׁ, שֶׁיִּשְׂרָאֵל הַקְּרוּיִם ״אָדָם״, נִשְׁמָתָם הִיא, לְמָשָׁל, כְּאוֹר הַנֵּר שֶׁמִּתְנַעְנֵעַ תָּמִיד לְמַעְלָה בְּטִבְעוֹ, מִפְּנֵי שֶׁאוֹר הָאֵשׁ חָפֵץ בְּטֶבַע, לִיפָּרֵד מֵהַפְּתִילָה וְלִידָּבֵק בְּשָׁרְשׁוֹ לְמַעְלָה בִּיסוֹד הָאֵשׁ הַכְּלָלִי שֶׁתַּחַת גַּלְגַּל הַיָּרֵחַ, כְּמוֹ שֶׁכָּתוּב בְּעֵץ חַיִּים. וְאַף שֶׁעַל יְדֵי זֶה יִכְבֶּה וְלֹא יָאִיר כְּלוּם לְמַטָּה, וְגַם לְמַעְלָה – בְּשָׁרְשׁוֹ, יִתְבַּטֵּל אוֹרוֹ בִּמְצִיאוּת בְּשָׁרְשׁוֹ, אַף־עַל־פִּי־כֵן, בְּכָךְ הוּא חָפֵץ בְּטִבְעוֹ. כָּךְ נִשְׁמַת הָ״אָדָם״, וְכֵן בְּחִינַת רוּחַ וָנֶפֶשׁ, חֶפְצָהּ וְחֶשְׁקָהּ בְּטִבְעָהּ לִיפָּרֵד וְלָצֵאת מִן הַגּוּף וְלִידָּבֵק בְּשָׁרְשָׁהּ וּמְקוֹרָהּ – בַּה׳ חַיֵּי הַחַיִּים בָּרוּךְ־הוּא; הֲגַם שֶׁתִּהְיֶה אַיִן וָאֶפֶס וְתִתְבַּטֵּל שָׁם בִּמְצִיאוּת לְגַמְרֵי, וְלֹא יִשָּׁאֵר מִמֶּנָּה מְאוּמָה מִמַּהוּתָהּ וְעַצְמוּתָהּ הָרִאשׁוֹן, אַף־עַל־פִּי־כֵן, זֶה רְצוֹנָהּ וְחֶפְצָהּ בְּטִבְעָהּ.
What it means is that the souls of Jews, who are called “man,” are, by way of illustration, like the flame of the candle, whose nature it is always to flicker upward, for the flame of the fire intrinsically seeks to be parted from the wick in order to unite with its source above in the universal element of fire which is in the sublunar sphere, as is explained in Etz Chaim. And although it would thereby be extinguished and emit no light at all below, and even above, in its source, its light would be nullified, nevertheless this is what it seeks in accordance with its nature. In like manner does the neshamah of man, including the quality of ruach and nefesh, naturally desire and yearn to separate itself and depart from the body in order to unite with its origin and source in G–d, the Fountainhead of life, blessed is He, though thereby it would become null and void, completely losing its entity therein, with nothing remaining of its former essence and being. Nevertheless, this is its will and desire by its nature.