I think you've got yourself worked up and its all psychological.
If you worry that you won't be able to perform, the stress from the worry makes it so you can't perform.
Take a deep breath, I am sure that if things don't go "perfectly" as you'd like when you are with your lady friend it won't be the end of the world. Give her lots of affection and foreplay and let things happen naturally. It will be alright. She and you will have a nice time together regardless of your performance so quit worrying about it and maybe when the time comes everything will be great.