Хасидус к Дварим 33:18

Simchat Torah is a preparation for the whole year, to be regular in Torah [study]. It is as the sages, may their memory be blessed, said, "[Thousands of scholars died] because they did not recite the blessing over the Torah first." And that is why Simchat Torah is at the beginning of the year, so that a person should contemplate the greatness of the Torah, since it is the words of the living God. And through the desire and joy in clinging to the Torah, there remains afterward a clinging from the occupation with Torah [study]. It is as it is written in the Midrash, "This is the blessing (Deuteronomy 33:1), that there be a blessing on the Torah before it and after it." And likewise, even merchants, who are not always occupied with Torah the whole year, nevertheless fix it in their hearts, and it becomes difficult to separate from the words of Torah, because of the joy [simchah] at the beginning of the year. This assists him not to completely forget it, even when he is occupied with other things. And it is written, Rejoice, Zevulun, in your going out (Deuteronomy 33:18). But it is difficult, as why should he rejoice in this portion? Rather, it is good advice: That through the joy before he goes out for trade, he is thereby guarded upon his going out. And that is why Simchat Torah is at the beginning of the year, as mentioned above.