I love to hear about that fresh excitement that comes with rediscovering horses. Ah, I remember it well . . . ..
You can't get confidence from a book and as you know, it comes as a by product of just doing the activity over and over and having predominantly successful experiences. So, in that vein, you want to have some challenges, but not so that you are overfaced from the get go. If you are an older rider coming back to horses you have to accept that you will be more cautious, probably more worried about falling, and less able to bounce back when you do fall (and assume that it WILL happen one of these days so that you won't be all shocked when it does). Cut yourself some slack and don't compare yourself to some memory of how you used to be.
Revel in each step you take as if you made that discovery all by youself and are the first to go there. Of course you are just followoing the steps of thousands, but since riding is learned by body experience, it's the FIRST for each and every one of us.
Good luck and let us know how it goes. You have been bitten and now you have become one of us! (think ,'invasion of the body snatchers or . . .)