shushan Purim: finishing the job

Why are we all celebrating today just because in Shushan and in Shushan alone they had an extra day to take care of our enemies? I think the answer has to do with a failure that has dogged our people since time immemorial -- the failure to finish the job. Whether it was Shaul's failure to finish off Amalek or Tzahal's most recent venture into Gaza, we always seem to pull back before the job is done, overcome by either our own innate sense of (misplaced) rachmanus or because of outside pressure and constraints. The Jews of Shushan did not leave things half-done by using only the one day everyone else had to fight our enemies; they made sure to take an extra day to finish the job. Perhaps this is why not just Shushan, but walled cities from the time of Yehoshua are included in this celebration. Had Yehoshua finished the job of conquering Eretz Yisrael, who knows how the rest of Jewish history might have turned out. We are in a sense still struggling to finish that original mandate of kibush and yishuv Eretz Yisrael. Let's hope we one day soon figure out how to finally complete that task.