A bird that dominates almost always develops negative behaviors like biting, fleeing, biting visitors, bonding with only one member of the family and attacking everyone else, etc. When I speak of assertive methods, I mean a very hands-on approach. I maneuver the bird into the situations it is avoiding long enough for it to discover that those situations are NOT threatening. Birds think they are taking the easy way out by fleeing and never get past that to realize how great life can be when they allow you to touch them. They won't volunteer to be exposed to new things.
Birds hate the unknown.
Flee from it, like the plague. I don't let a bird come out of the cage by itself. It soon learns the only way out is on my hand, or in some cases, a perch. How to get the bird out of the cage, how to keep it on your hand, how to get it to do step ups, how to get it to allow you to pet it, etc, are all teachable techniques. But not in an email.