Remember, you can't control other people's behaviour, but you can control the way you respond. Seek counselling if anger continues to be a big problem for you. Some times assertiveness gets a bad name because people confuse it with aggressiveness. But, if there were a yardstick to measure human behaviour, assertiveness would be right in the middle, with passiveness at one end and aggressiveness at the other. Here are some of the ways passive, assertive, and aggressive people come across to others.
Passive People Have trouble saying no.
Do whatever others ask, even if it's very inconvenient. Don't stand up for their rights. They're not even sure if they have any rights. Are taken advantage of. They get resentful but don't tell anyone.