I learned how hard hills are
By riding a route without any.
I rode 18 miles today and it was easy as pie. My legs barely feel like I rode, and I got going at a decent clip. Almost everywhere else I've ridden has had some hills, a few of which I've found to be challenging, but the veterans here would probably not think twice about.
That was incredibly encouraging to me.
Next ride I'm going to go a relatively flat route with some hills mixed in about halfway through.