Actual form does not match theoretical

Hi Alois,

I like to study and watch your videos over and over so that I know in my mind the correct/proper form and technique when doing strokes and footwork. It's been a year since I've been trying to put these theoretical knowledge in practice.

I've always assumed and thought that my forehand topspin stroke was almost "correct" and similar to what I watch in your videos. However, a friend of mine recently took a video of me doing forehand topspin drills and when I watched it, I found out that my technique was far from what I know in my mind! I'm a right hander and my shoulder on my non-playing arm (left) raises whenever I swing for a forehand stroke. I never knew that I unconsciously did this until I saw a video of myself playing. My legs are also quite stiff whenever I do the stroke. I was quite shocked that even though I can picture out the correct technique in my mind, I find that I don't do it in real practice. But whenever I try to practice the stroke in the mirror, I can do it correctly. Am I the only one that has experienced this, or is this a common problem for beginners? And what can I do to improve my Actual Form vs. Theoretical? Should I begin playing in front of a mirror? :)

Regards,

Carlo