You pay attention to the successes and failures of friends more than you do to those of strangers. You compare yourself to those who are close to you in order to judge your own worth. In other words, You know Barack Obama and Johnny Depp are successful, but you don’t use them to as a standard for your own life to the degree you do coworkers, fellow students, friends you’ve know since high school.
(Researchers) had students list the number of people they considered friends and then asked if the subjects believed they had more friends than did their peers and more friends than the average student. Thirty-five percent of the students said they had more friends than the typical student, and 23 percent said they had fewer. This better-than-average feeling was enhanced when considering their peers- 41 percent said they had more friends ship than did the peers they considered to be their friends. Only 16 percent said they had fewer. On average, everyone things they are more popular than you, and you think you are more popular than them.
Sure, some of your faults are just too obvious, even to you but you compensate for those by inflating what you like most about you. When you compare your skills, accomplishments, and friendships with those of others, you tend to accentuate the positive and eliminate the negative. You are a liar by default, and you lie most to yourself. If you fail, you forget it. IF you win, you tell everyone. When it comes to being honest with yourself and those you love, you are not so smart
David McRaney, You are Not so Smart