I am loud. I am sometimes obnoxious. I am overly energetic at times. However, none of those things makes me assertive. I have stood in line behind people I am pretty certain had passed away. I have asked permission from a dog. I have apologized to a wall I bumped into. Assertiveness is just not my nature.
I am practicing with little things. Occasionally I say "no" without going into a 2-hour explanation. I have actually realized that I can change lanes when I am the only person sitting behind a stalled car. And sometimes I don't apologize for things that aren't my fault.
This will be a slow and ridiculous process, but I have found a resource that I think will help. If you need help too, take a peek at this cool pdf from some folks in Australia. Maybe we could work on this together! If you don't mind...