One simple lesson to be learned is that you cannot jump to conclusions.
Reb Yakov Kaminetsky related that as a child, while he was once on his way to Yeshiva, an old woman needed his help. He was always on time, but on this day he came late. When his Rebbi asked why he was late, he told him exactly what had transpired. The Rebbi refused to beleive him and he was punished. Reb Yakov said that this story always bothered him. Here was a boy that was known to always tell the truth and never came late. Why and how could the Rebbe punish him without knowing of any wrong?