כִּ֧י כָל־יָמָ֣יו מַכְאֹבִ֗ים וָכַ֙עַס֙ עִנְיָנ֔וֹ גַּם־בַּלַּ֖יְלָה לֹא־שָׁכַ֣ב לִבּ֑ו גַּם־זֶ֖ה הֶ֥בֶל הֽוּא׃
For all his days are pains, and his occupation vexation; yea, even in the night his heart taketh not rest. This also is vanity.
Read kabbalistic (mystical) interpretation of Ecclesiastes 2:23: and classical mystical sources.