On Rosh Hashanah night, we eat simanim, such as an apple dipped in honey, among other simanim.
The origin of this custom is the Gemara (Krisus 6), which states, הוא מילתא סימנא, symbolic signs have significance.
Eliyah Rabba (quoted in Mishnah Berurah) writes, "The Shlah teaches that these signs remind the person to rouse himself to teshuvah and to daven for these matters."
Reb Shlomo Kluger (Chochmas Shlomo) writes, "Eating these foods isn’t a tefillah. Eating is never a tefillah. Rather, we eat these foods to show our trust that Hashem will give us a good year...and we say on them [that it should be a good year]. If chas veshalom there was a harsh decree, it will be turned for the good through our words. Amen, so shall be His will." Words are powerful. Saying it will be a sweet year is like a prophecy, which has the power to be fulfilled.
Reb Shlomo Kluger adds, "On Rosh Hashanah, after shacharis, one should say, כל עביד לטב רחמנא דעביד מה, 'Everything Hashem does is for the good.' 'לטובה זו וגם' And this is also for the good.' Such words turn things over that everything will indeed be good."
The ultimate siman is to be happy on Rosh Hashanah. The Mishnah Berurah writes, "We do simanim as a good omen. Therefore, it’s obvious that one must be cautious not to become angry on these days. In addition to the severe sin, one must make a good sign for the new year. He should be happy and trust in Hashem."
People in Yerushalayim would say, "If an apple dipped in honey is a sign of a sweet year, certainly, if a person is a ‘sweet Yid,’ by keeping a smile on his face and by greeting others warmly, what better omen can there be for a sweet new year?"
