#1.) You stay quiet when you should say something. If you let a text, an email, or a Facebook post go by without responding . . . even when no response is required . . . you might be offending someone. People just don't like to be ignored. When they don't get a reaction, it's like you're telling them they don't matter.
#2.) You accidentally remind people how you're better than them. Like when you tell a funny story about a drunken hookup . . . to a single parent who hasn't been on a date in years. It doesn't matter that you didn't mean it that way. They'll still resent you.
#3.) You don't realize you owe someone. This one might not be your fault. Sometimes people THINK they've done a lot more for you than they really have. But they'll still be angry when you don't repay the favors. You hear this one a lot after a relationship ends. Both people think they did more for their ex than their ex ever did for them.
#4.) You waste people's time. This one's tough too, because when someone's too busy to help you with something, they might not TELL you . . . since they don't want to SOUND like they're more important than you.
#5.) You don't realize you have an unfair advantage. When different minorities talk about equal rights, sooner or later, you hear someone else say, "I don't hate anyone . . . I just don't want anyone to get SPECIAL TREATMENT."