Another good reason for playing a 4 octave scale every day from slow to fast, according to my teacher at today's lesson, is that at least once each day you'll get all over the fingerboard, play slowly with rich sound and full vibrato, and also fast. Because some days what you practice otherwise may short one or more aspects of basic technique. For me, I am at my most zen when I'm playing my scale. I can sink into the physicality of cello playing without the distraction of new notes to learn. Everything goes better on a good scale day. And if I can't get it in tune, or I'm too tense because I'm distracted by something else, it's probably best to just stop there and come back to the cello later when I am in a better frame of mind.
Today at my lesson I only worked on the Prelude to the 2nd suite. I had a few moments of insight where I realized that I am trying too hard. And many more moments of frustration that without trying the notes elude me. One of my teacher's studio rules is that you come in when you get there, and great if you're there for part of the preceding student's lesson. And you are welcome to stay into the next lesson as long as you like. It just happened that the student following me both last year and this is the same high school sophomore. Last year she was working on the Saint-Seans concerto, and this year on Lalo, as well as Lee, Grutzmacher, and Duport etudes that are still well in my future. It is so incredibly valuable to see a more advanced student learning. Not only do I get a taste of the "next" technique, but I see both her and my teacher applying the technique that I am currently learning so that I can build on it in the future, without the distraction of my own playing.