He who fixes his eyes on his cup, the whole world seems to him like a mirror.
The drunk or drunkard does not see the mountains and valleys, but everything seems to him as one flat surface. In the question: Addiction to drinking causes the loss of the ability to see reality as it is (he gave his eye to...the meaning of the matter. His glass means his glass of wine).
("For he who sets his eye on the cup will walk uprightly (Proverbs 23) Rabbi Ami and Rabbi Assi, one said: Everyone who sets his eye on the cup - all the cities are like unto him as a straight path. And one said: Everyone who sets his eye on the cup - the whole world is like unto him as a straight path" - Yoma 8:1)
Translation
Expression (Hebrew)
הַנּוֹתֵן עֵינוֹ בְּכוֹסוֹ כָּל הָעוֹלָם דּוֹמֶה עָלָיו כְּמִישׁוֹר
Definition (Hebrew)
הַשִּׁכּוֹר אוֹ הַשַּׁתְיָן אֵינוֹ רוֹאֶה אֶת אֶת הֶהָרִים וְהַבְּקָעוֹת אֶלָּא הַכֹּל נִרְאֶה לוֹ כְּמִישׁוֹר אֶחָד שָׁטוּחַ. בְּהַשְׁאָלָה: הַהִתְמַכְּרוּת לִשְׁתִיָּה גּוֹרֶמֶת לְאִבּוּד הַיְּכֹלֶת לִרְאוֹת אֶת הַמְּצִיאוּת כְּמוֹת שֶׁהִיא (נָתַן עֵינוֹ ב...מַשְׁמָע הִתְעַנְיֵן.כּוֹסוֹ מַשְׁמָע כּוֹס הַיַּיִן שֶׁלּוֹ).
("כִּי יִתֵּן בַּכּוֹס עֵינוֹ יִתְהַלֵּךְ בְּמֵישָׁרִים(מִשְׁלֵי כג) רַבִּי אַמֵּי וְרַבִּי אַסִּי, חַד אָמַר: כָּל הַנּוֹתֵן עֵינוֹ בְּכוֹסוֹ - עֲרָיוֹת כֻּלָּן דּוֹמוֹת עָלָיו כְּמִישׁוֹר. וְחַד אָמַר: כָּל הַנּוֹתֵן עֵינוֹ בְּכוֹסוֹ- כָּל הָעוֹלָם כֻּלּוֹ דּוֹמֶה עָלָיו כְּמִישׁוֹר"-יוֹמָא עה ע"א)