Practice 6 hours a day!?
Yes! Practice 6 hours a day, and you will get better! Really? The truth is, just because you practice 6 hours everyday for the next 10 years does not mean you are going to improve a lot. And that is not because you are not talented or gifted. That is because the quality of practice is not there.
Practice with purpose
You should never practice just to practice. If you are practicing, that is because you have a specific goal to accomplish. And we are not talking about a performance in a recital in 3 months. We are talking about a goal that you set for the next 10 minutes, 30 minutes, or the end of the day.
Generally, the more specific the goal, the better the outcome will be. Say, "I will learn this page in the next hour." That is not a bad goal, but "I will spend the next 5 minutes learning the 1st line of this page starting with notes and rhythms, then the following 5 minutes I will tweak the accuracy of intonation and rhythm, then spend another 5 minutes to work on musical phrasings." This way you are targeting more specific goals at every minute of your practice which enables you to pinpoint your focus. A big problem about having a broad goal is that you need to sort out many things along the way all at the same time. By setting more specific purpose for your practice, you are narrowing down the number of issues you need to deal with at a time. It is easier to work on one issue rather than 10 simultaneously.
Keeping focus during your practice session is another important thing to keep in mind. You can accomplish so much more if you are focused. It is important to create an environment where you can focus when you practice. If something is keeping you from focusing, try to take care of it before you practice. If you can't focus because you are thinking about texting someone, then text now so you don't have to think about it. Clean up your room now if you can't focus because your room is messy. Get rid of factors that keep you from focusing as much as you can.
Then, there are times you just have to practice with all kinds of distractions. Knowing how to cope with distractions and stay focused is an important skill as a violinist. Distracting thoughts may come to your mind when you are performing in public, and when that happens you just need to deal with it on the spot. So it's good to know how to bring your focus back if distracted, and also we need to learn how not to get distracted during our daily practice so those distractions won't get in your way of a performance.
When you go to a lesson, your teacher points out what you are doing wrong, or areas you can improve on. One of the jobs teachers have at a lesson is to help students notice things they can do better to improve their violin playing. Unfortunately, teachers are usually only available to you once or twice a week. They can not help you point things out everyday for you. That means for the rest of the week, it is up to you to be aware of what you are doing or not doing. This is "self-awareness" in a practice. You want to be aware of what you do and don't do well. This is important because if you are aware you would know what you should be working on. Once you know what you have to work on, you come up with a way to solve the issue. You must be paying close attention to everything you are doing in order for you to be aware of yourself. Self-awareness makes a big difference in the quality of your practice and performance.
When you are practicing you have to be your own teacher, a very strict teacher. When you catch yourself doing something wrong, stop there and work on it before you move on. If you are playing out of tune, don't let it go. Be a good teacher to yourself, practice it before you go on unless your practice goal lies somewhere else and ignores the imperfection of the pitch at the moment.
Ask yourself "What would my teacher say if I play like this to her?" If your answer is "She will say, good!" that's great, but if not let's practice that.
Don't go easy on yourself. It is not always fun to be tough on yourself, but you will be rewarded later if you are critical to your own playing. On the other hand, if you are not critical you will let go things such as intonation and tone. It is not a big deal for a day, but when it goes on for months and years, there will be a consequence and you won't like it.
Sometimes it is good to assume that everything you are doing is wrong. Pretend that you are playing all the notes out of tune, all the musical phrasings wrong, etc. You will be amazed how keen your senses become. You will notice more details in your playing, both good and bad. What seemed normal before doesn't sound too good anymore, you will notice what sounded in tune before is not really in tune anymore. You will find many things you could be working on this way.
Tie them all together
Now it's time to put them all together. All of the things we looked at here are related to each other. If you don't have a purpose for the practice you are not focusing. If you are not focusing you are not aware of your playing. If you are not aware of your playing you can't be critical. If you are not being critical the purpose of your practice is not there. You see how they all come together? Thinking about all these things when you practice is far more important than to just practice for 6 hours a day. You can accomplish a lot in a short amount of time when you put all these into practice.