yeah nerves can be hard, theres a saying if your not nervous you dont care, which is pretty true
id advise having a couple of plans, or just "im going to go enjoy being with this woman(s)" mindset, so if no hard on, just cuddle and kiss or something, so your not panicing about not getting hard, and still enjoying yourself.
a hug tends to really lower nerves too.
and you dont need to impress her or be a porn star worthy performance, just be a nice version of yourself.