Performance anxiety?

 I usually try and practice all my pieces every day. I mostly perform them all right. However, when I go to my teacher's house for 30 minutes per week, I often stumble and play the wrong notes. Is it because I am playing on an instrument (a Harry Hobbs upright acoustic piano) that is not mine (a Yamaha digital piano)? Or is it because of performance anxiety?

Music theory workbooks

I had started doing the ABRSM's Discovering Music Theory Grade 1 Workbook from June 2024. Today I completed doing the workbook on my own and placed an order for workbooks 2 and 3. It is not as if my teacher told me to do this but I bought the workbook Grade 1 and Eric Taylor's AB Guide to Music Theory Part 1 in June and did it in order to understand things better. I think doing the workbook has definitely helped me learn the theory better.