I think a big part of getting to know your ride is not only of the bike itself, it's knowing the roads and routes you take.
A few weeks back I cycled to meet a mate at the Gorge for the ToB that was passing through Cheddar Gorge. On the way, down Shipham Hilll - a long descent down into Cheddar - there was a cyclist in front of me caning it down. Now, it was pretty awesome but not stupid or irresponsible. I caught up with him later and congratulated him on an awesome descent and then realised that I'd only descended this hill twice before and if it had been the Gorge itself, that I know very well, I may have been more confident at his kind of speed. Then I realised that the only criterium I'd employed for measuring my own speed was someone else, on a hill I wasn't used to. A recipe for disaster methinks.
So, get to know the routes you take on your road bike and soon enough you'll gain confidence enough on those routes, hills, descents to teach you a bit more about how your road bike differs, if at all.
Of course, little things can still give you the jitters. I bought my carbon earlier in the year and for various reasons couldn't ride it for the first few months but soon got the handling and elements like the brakes served to induce me with more confidence. But, I had a nasty blowout a few weeks ago now, on a descent, round a bend, nearly lost control of the bike, and I treat that particular place with slightly more respect than perhaps I did.
Only you know your own limit and it changes with confidence and that confidence, I believe, is also about knowing your road as much as the bike.