To stew in one's own juice
By analogy: Thought over and formed positions without revealing them to other opinions. Was occupied with himself or his creation while disconnected from the surroundings.
(Modern Hebrew)
Translation
Expression (Hebrew)
הִתְבַּשֵּׁל בַּמִּיץ שֶׁל עַצְמוֹ
Definition (Hebrew)
בְּהַשְׁאָלָה: חָשַׁב וְגִבֵּשׁ עֲמָדוֹת לְלֹא שֶׁנֶּחֱשַׂף לְדֵעוֹת אֲחֵרוֹת. הָיָה עָסוּק בְּעַצְמוֹ אוֹ יְצִירָתוֹ תּוֹךְ נִתּוּק מֵהַסְּבִיבָה.
(הָעִבְרִית הַחֲדָשָׁה)