/gemar chatimah tovah/
“Indeed, although Yom Kippur is the most solemn day of the year, it is suffused with an undercurrent of joy; it is the joy of being immersed in the spirituality of the day and expresses confidence that G‑d will accept our repentance, forgive our sins, and seal our verdict for a year of life, health and happiness.” from “How to Observe Yom Kippur 2018” (Chabad.org)
“Shanah tovah u’metuka” (שנה טובה ומתוקה) — a sweet good year to you!