R. Moshe Chaim Luzzatto opens Mesillat Yesharim with the quality of Zehirut (watchfulness/guarding), which is functionally the ethical and spiritual equivalent of Shamor — constant vigilance against transgression and the guarding of one's actions.
בְּבֵאוּר מִדַּת הַזְּהִירוּת הִנֵּה עִנְיַן הַזְּהִירוּת הוּא שֶׁיִּהְיֶה הָאָדָם נִזְהָר בְּמַעֲשָׂיו וּבְעִנְיָנָיו, כְּלוֹמַר, מִתְבּוֹנֵן וּמְפַקֵּחַ עַל מַעֲשָׂיו וּדְרָכָיו, הֲטוֹבִים הֵם אִם לֹא, לְבִלְתִּי עֲזֹב נַפְשׁוֹ לְסַכָּנַת הָאֲבַדּוֹן חָס וְשָׁלוֹם וְלֹא יֵלֵךְ בְּמַהֲלַךְ הֶרְגֵּלוֹ כְּעִוֵּר בַּאֲפֵלָה. וְהִנֵּה זֶה דָּבָר שֶׁהַשֵּׂכֶל יְחַיְּבֵהוּ וַדַּאי. כִּי אַחֲרֵי שֶׁיֵּשׁ לָאָדָם דֵּעָה וְהַשְׂכֵּל לְהַצִּיל אֶת עַצְמוֹ וְלִבְרֹחַ מֵאֲבַדּוֹן נִשְׁמָתוֹ, אֵיךְ יִתָּכֵן שֶׁיִּרְצֶה לְהַעֲלִים עֵינָיו מֵהַצָּלָתוֹ,
The idea of watchfulness is for one to be cautious of his deeds and matters, namely, contemplating and watching over his deeds and ways whether they are good or evil; not abandoning his soul to the danger of destruction, G-d forbid, and not walking through the course of habit like a blind man in darkness. Reason certainly obligates this. For after a person has knowledge and reason to save himself and escape from the destruction of his soul, how is it conceivable that he would willingly blind his eyes from saving himself?!