A lot of us, if not most of us, tend to be overly critical of ourselves. Myself included. Up until 5 months ago I had no idea that I could pass, until a random person had absolutely no idea that I was trans in a large group of outted trans people, he just thought i was a lesbian there supporting the trans community.
Up until that point I was insanely critical of myself, and I had myself too terrified to go out. We cannot really be our own judge on our own transitions. Because no matter how much we may want our changes, we tend to look back at ourselves and see how things used to be, even if we really aren't that way anymore. Best thing you can do is to get someone who is neutral to give you their honest opinion.
And yes you improve with experience. As you cut lose from your old shell don't be afraid to express yourself the way you want. But at the same time don't try to force things on you that you aren't really feeling just because you think it's what a girl should do. You need to develop into who you were meant to be, not what you think you want to be. You'll be much happier that way!
I still need to work on my voice a bit, if I try hard enough i can get maam'd on the phone or at a drive through, but I often don't make mental notes about what I did to achieve that voice.
Anyways, went off on a bit of a tangent. Hope I was able to help.