Making a good impression is not something "useless". As a believer of Islaam, it is crucial that when interacting with non-Muslims (or sometimes even Muslims), one must keep in mind that he or she is not only representing his or her own self, but he or she is also representing one's family, country, culture, but at UTMOST importance, a Muslim represents Islaam.
Don't freak out if you're excluded at Immigration or your neighbors give you bad looks. Other people's actions should never effect yours. You're a Muslim, thus a believer of the Qur'aan and of all the suwar (Surahs) in the Qur'aan, including Surah Fussilat (AKA Surah HaaMeem Sajdah) and Ayaat 33 through 35:
(33) The good deed and the evil deed are not alike. Repel the evil deed with one which is better, then lo! he, between whom and thee there was enmity (will become) as though he was a bosom friend. (34) But none is granted it save those who are steadfast, and none is granted it save the owner of great happiness. (35) And if a whisper from the devil reach thee (O Muhammad) then seek refuge in Allah. Lo! He is the Hearer, the Knower.