In this week's parsha we read, "For you are a holy nation unto Hashem" (Devarim 14, 21). The Sifrei has an interesting commentary on these words: "Make yourself holy with regard to things that you permit. If you are of the opinion that a specific thing is permitted, nevertheless, when you find yourself in the company of those who forbid it, you should not permit it in their presence."
Rav Wolbe (Alei Shur vol. I pg. 137) comments that if it were up to us to describe what is wrong with permitting something in the presence of those who forbid it, we most probably would have focused on a different angle. We would understand that such behavior is improper because one is not taking into account the feelings of those who act stringently. Moreover, he might even cause them to henceforth disregard their stringency due to his actions.
However, it is clear from the Sifrei that states, "Make yourself holy" that the focus is not on those who act stringently; rather on the one who wishes to permit the stringency. The Sifrei is revealing an incredible aspect of kedusha (holiness). When one finds himself in the company of those who are more vigilant, this should arouse a desire to emulate them at least for the duration of time that he spends in their presence!
This aspect of kedusha can be defined as "applying that which one perceives around him to himself." In a similar vein Chazal tell us, "He who sees a sotah in her state of degradation, should abstain from wine" (Sotah 2b). The Torah is telling us that instead of decrying the perpetrator and the terrible transgression committed, one should direct his focus inward and concentrate his efforts on ensuring that he himself never commits such a sin.
It was this fault that Chazal (Bamidbar Rabba 16, 5) attributed to the meraglim. Even though they had seen what happened to Miriam when she spoke derogatorily about Moshe Rabbeinu, they failed to apply the lesson to their own personalities.
A wise man not only learns from the mistakes of others, he learns from everything that occurs to others. The Baal Shem Tov would say that everything a person sees is to be taken as a message from Hashem as to how we ourselves appear. If we see something, we were meant to see it in order that we take a lesson from it. Instead of getting annoyed at the fellow who double parked his car, we should think of the many instances where we are guilty of similar behavior (even if not to the same degree of insolence). This is not only the proper outlook on life with regard to improving one's character; it also has numerous benefits regarding ones bein adom l'echaveiro!