The way in which one acts towards others determines the way in which Heaven will act towards him…As our Sages state “Whoever has compassion towards others will be shown compassion from Above” (Shabbos 151b); and “Whoever refrains from exacting his measure [of retribution from others for the wrong they caused him] will have all his sins forgiven (Rosh Hashana 17a).
~ Sefer Shmiras Halashon