I took lessons for 10 years growing up - I would ride just about any horse and was confident. I'm in my late 20s now and haven't ridden much in 7 years. I've taken lessons off and on, only for a few months at a time (then something seems to happen so I have to quit for a while). I feel like a complete beginner again! I'm not confident and I don't have the muscle tone to do what I want. It's very frustrating to know that you used to be able to do something, but now feel you can't. The professionals I've ridden with said I had a great seat and looked very good, so I know the skills are still there and I'm sure yours are too. I don't think we'll ever be as confident as when we were teenagers, but in general your confidence should come back in time. You certainly weren't confident when you first started riding and you took things slow - just go back to that mentality instead of expecting your body to do what it used to do right away.
that's exactly how I feel. Good advice :) thanks!