The idiographic approach to understanding other's personalities is something I've learned in this Psychology 1001 course that has stuck with me. Previous to learning this, I never actually considered how someone's personality could affect their day-to-day lives. This concept has helped me understand that because someone you run into throughout your day/ in your life is different than you, does not mean you should judge them. They're background, family history, and personal experiences have had an impact on their personality and may have altered who they are as a person.
Personality differences in people represent the different upbringings and life experiences each of us has throughout our life. Without these unique experiences, everyone would be a carbon-copy of another personality-wise. Our life stories shape our different personality traits creating an interesting world.
I've learned that it is unfair to judge someone based on their behaviors without having an understanding of where these behaviors stemmed from. Only after knowing someone's life story or "walking a mile in their shoes" would it then be fair to judge their actions.