You have vexed someone with stupid questions, boring ideas, or by unwanted advice;
You have insulted someone by making unpleasant and rude statements regarding his/her religious beliefs, political outlooks, or aesthetic tastes;
In one way or another you have rushed into someone's private world, subjecting to unacceptable criticism things that he/she cares about.
You have refused to give back borrowed money or you have denied to pay someone a well-earned reward;
You have been denied sexual intimacy due to your slovenliness, bad manners, or lack of personality;
People just don't like your company - this also happens.