The Talmudic tractate Avot states: "Rabbi says, 'What is the straight path that a person should choose for himself?' It is the path that is good for both himself and those around him." That is, the path of the "golden mean" is the straight path.
However, when it comes to modesty or egoism, Avot recommends not the "middle" but the extreme: "Rabbi Levitas of Yavneh says: 'Be humble in the highest degree, for the hope of man vanishes'" (Avot 4:4).
Therefore, the sages taught: a person must be modest in his actions—with his father and his mother, with his teacher, with his wife and children, with those near and far, and with a non-Jew in the marketplace—in order to be loved in Heaven and pleasant on Earth (Tana Dvei Eliyahu).