On Shabbat, the Melitzer Rebbe shlit'a told me the following beautiful story, passed down from father to son from his great great grandfather Rebbe Meir'l of Promiszlan; Keep it in mind before allowing yourself the "luxury" of feuding with a fellow Jew:
Serving the same G-d
Rebbe Meir'l of Promiszlan and Rebbe Yitzchok of Strettin were engaged in a long, drawn-out feud. Knowing that dissension serves no purpose, Rebbe Meir'l approached Rebbe Yitzchok and attempted to make peace. The latter only turned his face to the wall. "Please, Strettinner Rebbe, allow me to tell you a tale," said Rebbe Meir'l, and told him the following story:
During the time of the Spanish Inquisition, a Marrano* suspected of secretly being Jewish became deathly ill. The Inquisitors called the local priest, and told him to go see if the dying man would make last confession, proving that he's a Catholic, or else otherwise be burned at the stake as a Jew. The Priest and the Henchman entered the sick man's room, and the sick man turned his face to the wall, refusing to reject his true faith in Hashem during his last minutes on earth.
The Inquisitors said, "Ahah, he's a secret Jew!" The priest said no, he's embarrassed to confess in front of others. Everyone must leave the room!
Only the dying man and the Priest remained in the room. The priest, a Marranno himself, whispered in the man's ear, "You can say Shma Yisrael now, and express your belief in Hashem before you die. You no longer need to turn your back on me, because we both serve the same G-d." With his dying breath, the Marrano utterred, "Hear O Israel, the Lord our G-d, the Lord is one!"
"So you see, Strettinner Rebbe," said Rebbe Meir'l, "You no longer have to turn your back on me, because we serve the same G-d!" The feud ended on the spot.
*Marranos - the Spanish Jews who posed as Catholics on the outside, and secretly continued to practice their Judaism behind closed doors