I am still trying to find ways and understand how to not be passive as a person in general to 180 myself.
Are you going to IC? They can really help you with that. I was a passive person too and I am changing it up for myself and it is really awesome.
Things that I focus on:
1. Stand up for myself without worrying about how the other person will react. 2. Be more assertive about what I want and what my needs are. 3. Don't be wishy washy - say what you want to do and when. 4. Not avoiding conflict - handling it with poise and calmness.
Do all of those things without being rude, cold, and passive aggressive, demeaning, or mocking. Exude self-confidence and emotional control. Also do those things but create enough space to work with others.
This will not only help you get out of being passive, it will also get you mad respect from people.