Chazal say (Bava Metzia 30b) that Yerushalayim was destroyed because they upheld the law of the Torah. The gemara explains this shocking statement by saying that it means that they followed the law exactly as prescribed and did not look beyond the strict judgment to find a settlement amicable to both sides.
The Chofetz Chaim (Shaar HaZechira 2) asks that Chazal enumerated several aveiros that Klal Yisroel did that caused the Churban. That is inconsistent with this gemara. He answers that, indeed because of those aveiros the Churban was warranted. However that was the strict Din. Hashem can act Lifnim Mishuras HaDin, with tolerance beyond what the strict din calls for. However this is only if the people act Lifnim Mishuras HaDin as well. Since they didn't do so and instead dispensed judgment without any mercy, Hashem had no choice but bring upon them the full force of judgment.
If you are Mivater and look past your "rights" and show mercy to someone who offends you in any way, Bais Din Shel Ma'ala will do the same for you. Unless you are Tzaddik Gamur, it sounds like a very good deal!
"Zachor Eis Asher Asa Hashem L'Miriam BaDerech B'Tzaischem MiMitzrayim"
The Ramban and other Rishonim count among the Mitzvos Aseh Min HaTorah the mitzva of remembering and saying with your mouth each day what Hashem did to Miriam when she spoke about her brother Moshe. The Chofetz Chaim in Shaar Tvunah Perek 12 says that being Mikayem this mitzva can save you from the aveira of Lashon Hara. More than just saying the pasuk, says the Chofetz Chaim, one must think about the incident in order for it to have its intended effect.
Listen to our Shemiras HaLAshon Yomi in our audio section. Two halachos a day according to the Luach.