You have to be an artist in multitasking when you play the violin. You have to concentrate on your hand grip, where your fingers must press, your intonation, your tone production, and your posture while making sure that your bow stays on your ring tone and maintains a straight bowing motion.
The first thing my previous teacher concentrated on while I was having my lessons then in a multipurpose hall in the University of the Philippines (no, it was not an official U. P. course) was my bowing. My bow will go on an angle and skid over the strings like a threadbare tire on wet asphalt. And the main issue why I can't keep my bowing straight is because of my wrist. Yes, my wrist.