What "taking it personally" actually means
It means reading an event as a statement about you: your worth, your standing, whether you're wanted. A short reply becomes "they're annoyed with me." A meeting you weren't invited to becomes "I don't matter here."
It isn't self-centeredness, and it isn't the same as narcissism. Most people who take things personally are very aware of other people. They're just quick to assume the worst about where they stand.