וְלָבוֹא לְשִׂמְחָה הוּא עַל־יְדֵי מַה שֶּׁמּוֹצֵא בְּעַצְמוֹ אֵיזֶה נְקֻדָּה טוֹבָה עַל־כָּל־פָּנִים, כַּמְבֹאָר עַל פָּסוּק: אֲזַמְּרָה לֵאלֹקַי בְּעוֹדִי (בְּלִקּוּטֵי הָרִאשׁוֹן, בְּסִימָן רפב), עַיֵּן שָׁם. 3. The way a person achieves joy is by finding in himself at least some good point, as in the explanation of the verse “I will sing to God with the little I have left” (Psalms 146:2; Likutey Moharan I, 282). See there.
וְעַל־כָּל־פָּנִים יֵשׁ לוֹ לִשְׂמֹחַ בַּמֶּה שֶׁזָּכָה לִהְיוֹת מִזֶּרַע יִשְׂרָאֵל, שֶׁלֹּא עָשַׂנִי גּוֹי, וּכְמוֹ שֶׁאָנוּ אוֹמְרִין: בָּרוּךְ אֱלֹקֵינוּ שֶׁבְּרָאָנוּ לִכְבוֹדוֹ, וְהִבְדִּילָנוּ וְכוּ' וְנָתַן לָנוּ תּוֹרַת אֱמֶת וְכוּ'. מִכָּל זֶה וְכַיּוֹצֵא בָּזֶה רָאוּי לוֹ לִקַּח לוֹ שִׂמְחָה לְשַׂמֵּחַ דַּעְתּוֹ כַּנַּ"ל. No matter what, a person can rejoice that he is privileged to be from the seed of Israel—“for not having made me a gentile”—and as we say: “Blessed is our God, Who created us for His glory, separated us… and gave us the Torah of truth….” It is fitting that he be happy about all this and similar such things in order to gladden his mind.
וְזֶה בְּחִינַת (שבת עז:): בְּדִיחָא דַּעְתֵּהּ, שֶׁהוּא דָּבָר גָּדוֹל, דְּהַיְנוּ שֶׁמְּקַשֵּׁר הַשִּׂמְחָה לְמֹחוֹ וְדַעְתּוֹ, וַאֲזַי הַמֹּחַ מְשֻׁחְרָר, וְיֵשׁ לוֹ יִשּׁוּב־הַדַּעַת כַּנַּ"ל, וְגַם לְמַעְלָה נַעֲשֶׂה מִזֶּה יִחוּד גָּדוֹל עַל־יְדֵי בְּדִיחָא דַּעְתֵּהּ: This is the meaning of “of a jovial mind” (Shabbat 77b), which is a great thing. It refers to his binding joy to his mind and daat, so that with the mind set free he attains yishuv ha-daat. And also on high, a great unification is made by his being “of a jovial mind.”