When students come to me for piano lessons, the first thing I do is teach them to sit at the piano properly. This is often not what a student wants.
Students want to play their favorite songs immediately, and I can see why they would want to do that, but first we have to learn to walk, so how to sit at the piano comes first.
I had a reminder of why you must sit properly at the piano when playing piano recently, in fact, a very painful reminder. We don't always do what we preach. I wish I had followed my own advice.
A few months ago I was filming a number of piano lessons that took several weeks to complete. In order to get the camera angles to work, I had to lower my seat to a completely wrong position for playing the piano. If a student sat like this I would be very unhappy. But hey, this is me I know what I am doing, I am an expert, I will be fine. The recording took many hours a day for a quite a few weeks. I woke one morning to find I had a sore shoulder, this progressively worsened to the point I could not lift my arm to the horizontal position.
Eventually, I realized that my seating position was the problem. By re-positioned my seat where it was and should be, slowly my shoulder has improved considerably. A painful experience easily prevented by following my own advice.
A second point is that I noticed my own piano playing had also suffered and was not up to par. So I have to redo all the filming done previously. Don't make my mistake, always sit properly at the piano.
I have a post showing how to sit at the piano that I did some time ago. It will help you sit at the piano properly.