126:4 One should be careful not to watch the hunts of the non-Jews, nor their dances and other celebrations. If one should hear the sounds of their celebrations, he should sigh and be sad over the destruction of Jerusalem, and he should daven to Hashem on behalf of Jerusalem. One may not attend even a hunt organized by Jews because this is considered a gathering of scornful people (see Psalms 1:1). All kinds of joy are prohibited except for bringing joy to a groom and bride, whether through singing or musical instruments. Even there, however, one should not overdo things. A person is not permitted to fill his mouth with laughter in this world, not even for the joy of performing a mitzvah, as per Psalms 126:2, “then our mouths will be filled with laughter” (“then” referring to future Messianic times).
127:1 Just as it is a mitzvah for the public to fast and pray for any misfortunes that might occur, it is likewise a mitzvah for each individual to do so for any personal misfortunes. If someone has a sick person in his family, if he got lost on a journey, or if he was imprisoned on false charges, he is obligated to fast and pray to Hashem for mercy that He should save him. This is the way of repentance, so that a person should not think that misfortune just happened to him randomly. This is what is meant by Leviticus 26:27-28, “walk contrary to me…then I will walk contrary to you in fury.” This means that G-d will bring misfortunes upon us in order to encourage us to repent. If we think that things just happen to us by chance, G-d will increase misfortunes upon us in His fury. We need to recognize that our sins cause G-d to bring misfortunes upon us and we must search our deeds and return to Hashem so that He will be merciful to us.