Passive-aggressive people are filled with rage but are unable or unwilling to express their anger directly. Instead, they express it in sneaky, indirect ways. Typical negative passive-aggressive behaviours include lying, manipulating, blaming others for one's one mistakes, being late, procrastinating, sabotaging a job, giving people the silent treatment and being nice to people to their faces but talking negatively about them behind their backs. Passive-aggressive people are actually afraid of their own anger. They may have grown up in families where they were punished for expressing their needs and their emotions.
Become aware of your passive-aggressive behaviour. Many passive-aggressive people do not realise they are acting in a passive-aggressive way. You can't change your behaviour until you acknowledge it exists.
Develop empathy for other people. This may be hard for passive-aggressive people, who themselves may not have received enough empathy from their families when they were growing up, but it's an important step for passive-aggressive people to take.
Practice being assertive. Learn how to express your needs and how to say "no" without getting angry.
Make peace with your past. Learn to accept that your parents did what they could, given their own limitations. The more you can release anger that you still hold towards people from your past, the more you can avoid dumping that anger on other people in the present.
Find more positive ways to deal with situations that make you angry. Instead of fuming and fantasising about revenge, look for constructive ways to solve problems.