Your nervousness is perfectly understandable. You had a set of expectations for your performance and perhaps mentally prepared yourself to play under those circumstances, the circumstances changed and your brain couldn't adapt quickly enough. Remember that performance anxiety is something created by you, not the performance nor the people there. It is a mental distress signal at an event which you deem in your head to be important. No amount of physical piano practicing will help overcome performance anxiety if you suffer from it. It causes one to start paying attention to everything except the activity you need to do on stage.
First, how well did you know the piece? Where you relying mostly on muscle memory? If someone gave you a sheet of paper would you be able to write down the notes? Do you have to visualize your hands in order to see the music in your head or do you see the notes on the score? You need to approach your msuci learning process with more than just physical playing. Analyze the work harmonically (this way if you get lost you'll know whatkey you're in), work in small segments so that you can literally start from any measure of the piece while practicing.
A psychological problem (which most of us have grappled with) requires a psychological solution. You have to prepare your brain as well as your fingers for a public performance, without one of the two the probability is that you'll have problems. May I suggest you purchase a book called My eLssons with Kumi, written by composer Michael Colgrass (
https://www.michaelcolgrass.com). The book is dedicated to this specific issue and provides a variety of strategies for overcoing the anxiety and learning to channel it positively into your performance, whether it be music or speaking or whatever. Many memebers of this forum know I recommend it wherever I go. It really helped me get over all the detrimental nerves and I don't even do half of thebrain excercises the book suggests. Seriously, give it a try.
Keep in mind that, just like piano practice, mental practice will require some time and effort, but if you do it you will definitely feel and hear the results in your next performance. Mindless practicing on the piano for hours on end will not make a nervous performer any more secure. Work your brain, away from the piano, and prepare it for performance as well and you will enjoy performing much more and perform your best every time.
Elena
https://www.pianofourhands.com
Topic: disappointed in recital :-(