Being Confident
I learned to be confident from playing the violin because of the following components: string sound and performance. Even as a pianist, I find the sound of a string instrument to be more soothing. The beauty of the string is that with each stroke of the bow, you can vibrate the sound so it bounces rapidly in and out of the actual note, and also allow it to ring after the sound has been played. I believe string sound is naturally sweeter and more lovely than the banging of piano keys, and you can slide and shift along the string. I also find string sound to be more bass-y and as a result, it feels fuller and bolder. On the other hand, when I'm playing violin in front of other people, I'm putting on a performance for them, even in my lessons. I'm letting them watch me play, I'm letting them put their attention on me. There is a thrill with playing well, as it improves my confidence, and even if I don't play as well, it takes away confidence less than playing well builds it up, so I'm not losing more than I gain. A performance on violin usually has the performer standing up, and when I'm standing up, I can show that I'm confident by standing tall and leaning back a bit to open up my stance.
Listening
Violin builds my listening ability by allowing me to understand intonation. I talked about ringing sound in the string and the beauty of the ringing sound. This is the ultimate reason why intonation is so important. When the notes are in tune, the sound extends longer and is more musical as a result. The little things construct the big phrases and beautiful melodic lines, and they require attention. The attention needs to go to the dynamics, articulation, fingerings, and especially intonation. Violinists desire a stylistically correct approach and they work on it in practice. They listen to the sound they're producing, and they will fix it accordingly. No violinist likes to play a performance that is out of tune, so they take plenty of pride in having correct intonation. Violinists also learn to listen by hearing other people play, and they pick up any tendencies that are of considerable application to their own playing.
Open Heart
Violinists are putting on a performance. The performance is a culmination of the hard work and preparation to learn and polish the repertoire. An open heart means having the will to play for an audience who is aware of what the violinist has done to get ready. They are excited to hear me, and an open heart means that I am willing to give what I've got on a particular day, and not worry about anything that happens. An open heart allows me to take some critiques and coaching from others, whether they are my peers or instructors. They are making me better. An open heart tells me that I'll be exposed to mistakes but I'll correct them. An Open Heart is a combination of listening and being confident, which make up three things I learned from playing the violin.