Trying to improve/define/work on my confidence as a Dom

A lot of the advice already given in this thread is hella useful, but I will add a bit in about expectations.
With one of the first subs I ever had, I was really nervous for our first few times, both because I was inexperienced (they were as well) and because I felt like I had to live up to whatever expectations they had in mind for how I'd be.
And I think everyone sort of has these expectations naturally, or thoughts ahead of time on how they imagine things will be, but I voiced these concerns with my sub at the time and they were honestly surprised I was so nervous about that sort of thing. For the most part, they were just excited to experience things with me, regardless of how things were going to go.

I think it's important to remember that, yes, we all want to experience things and get certain things out of a relationship, but nobody has to meet any expectations. Your partner is probably just excited to get to be with you, regardless of how successful your scenes are or whatever.

And, on that note, it's worth telling your partner that you're nervous or unsure. It's ok to be cautious or unsure, and if they're cool, they'll be down to just try stuff out and not take things too seriously. It's unlikely they're going to judge your skills or whatever if they know you're still trying to get comfortable.